RP2040-code/Function Generator/FunctionGenerator.cpp

#include <stdio.h>
#include <string.h>
#include "pico/stdlib.h"
#include "pico/binary_info.h"
#include "hardware/spi.h"
#include <math.h>
#include "hardware/clocks.h"
#include "hardware/dma.h"
#include "blink.pio.h"
#include "FastDAC.pio.h"
#include "SlowDAC.pio.h"

/////////////////////////////
// Define GPIO connections...
/////////////////////////////

// Note: The SPI Port only works through specific pins, so this port is defined first.
// SPI Port connections...                          // ┌──────────┬───────────────┬─────────────┐──────────────┐
                                                    // │ PGA2040  │ Connection    │ MCP41010    │ Nixie module │
                                                    // ├──────────┼───────────────┼─────────────┤──────────────┤
#define PIN_RX          16                          // │ GPIO 16  │ RX/spi1_rx    │             │      -       │
//#define PIN_CS          17                        // │ GPIO 17  │ CS/spi1_cs    │             │              │ can this be re-defined ?
#define PIN_CLK         18                          // │ GPIO 18  │ CLK/spi1_clk  │             │  SCK (blue)  │
#define PIN_TX          19                          // │ GPIO 19  │ TX/spi1_tx    │             │  SDI (green) │
#define Nixie_CS        21                          // │ GPIO 21  │ Chip select   │             │  SS1 (white) │
                                                    // └──────────┴───────────────┴─────────────┘──────────────┘
#define SPI_PORT        spi0                        // These SPI connections require the use of RP2040 SPI port 0

#define _A               0                           // DAC channel alias
#define _B               1
#define LED             20                          // GPIO connected to LED
#define BitMapSize     256                          // Match X to Y resolution
//#define BitMapSize      360                       // won't work - DMA needs to operate as a power of 2
#define Slow             0
#define Fast             1
#define _Sine_           0                           // Permited values for variable WaveForm_Type
#define _Square_         1
#define _Triangle_       2
#define _GPIO_           0
#define _PIO_            1
#define _BM_start_       2
#define _SM_fast_        3
#define _SM_slow_        4
#define _SM_code_fast_   5
#define _SM_code_slow_   6
#define _SM_             7
#define _DMA_ctrl_fast_  8
#define _DMA_ctrl_slow_  9
#define _DMA_data_fast_ 10
#define _DMA_data_slow_ 11
#define _Funct_         12
#define _Phase_         13
#define _Freq_          14
#define _Range_         15
#define _DutyC_         16

unsigned short DAC_channel_mask = 0 ;                                       // Binary mask to simultaneously start all DMA channels
const uint32_t transfer_count = BitMapSize ;                                // Number of DMA transfers per event
int WaveForm_Type;
const uint startLineLength = 8;                                             // the linebuffer will automatically grow for longer lines
const char eof = 255;                                                       // EOF in stdio.h -is -1, but getchar returns int 255 to avoid blocking
int ParmCnt = 0, Parm[4] ;                                                  // Storage for 4 command line parameters
int SelectedChan, c, i = 0, dirn = 1 ;
const char * HelpText = 
"\tUsage...\n"
"\t  ?            - Usage\n"
"\t  S            - Status\n"
"\t  I            - System info\n"
"\t  <A/B/C>fnnn  - Frequency                  ( 0->999 )\n"
"\t  <A/B/C>h     - Frequency multiplier  Hz\n"
"\t  <A/B/C>k     - Frequency multiplier KHz\n"
"\t  <A/B/C>snnn  - Sine wave + harmonic       ( 0->9 )\n"
"\t  <A/B/C>qnnn  - Square wave + duty cycle   ( 0->100%% )\n"
"\t  <A/B/C>tnnn  - Triangle wave + duty cycle ( 0->100%% )\n"
"\t  <A/B/C>pnnn  - Phase                      ( 0->360 degrees )\n"
"\t  <A/B/C>w     - Sweep frequency\n"
"\t  <A/B/C>      - DAC channel A,B or Both\n"
"\t        nnn    - Three digit numeric value\n";

class DACchannel {

//   static void pio_sm_set_wrap ( PIO pio, uint sm, uint wrap_target, uint wrap )	

    unsigned short DAC_data[BitMapSize] __attribute__ ((aligned(2048))) ; // Align DAC data (2048d = 0800h)
    uint StateMachine[2] ;                                                // Fast and slow State Machines
    uint Funct, Phase, Freq, Range, DutyC;
    uint GPIO, _pioNum, SM_fast, SM_slow, SM_code_fast ;                  // Variabes used by the getter function...
    uint SM_code_slow, ctrl_chan_fast, ctrl_chan_slow ;
    uint data_chan_fast, data_chan_slow ;
    PIO pio;                                                              // Class wide var to share value with setter function

public:
    // Setter functions...
    void ReInit () {
        // Re-initialises DMA channels to their initial state.
        // Note: 1) DMA channels are not restarted, allowing an atomic (simultaneous) restart of both DAC channels later.
        //       2) Cannot use dma_hw->abort on chained DMA channels, so using disable and re-enable instead.
        //       3) This needs to be performed across both DAC channels to ensure phase sync is maintained.
        // Disable all 4 DMA channels associated with this DAC...
        hw_clear_bits(&dma_hw->ch[data_chan_fast].al1_ctrl, DMA_CH0_CTRL_TRIG_EN_BITS);
        hw_clear_bits(&dma_hw->ch[data_chan_slow].al1_ctrl, DMA_CH0_CTRL_TRIG_EN_BITS);
        hw_clear_bits(&dma_hw->ch[ctrl_chan_fast].al1_ctrl, DMA_CH0_CTRL_TRIG_EN_BITS);
        hw_clear_bits(&dma_hw->ch[ctrl_chan_slow].al1_ctrl, DMA_CH0_CTRL_TRIG_EN_BITS);        
        // Reset the data transfer DMA's to the start of the data Bitmap...
        dma_channel_set_read_addr(data_chan_fast, &DAC_data[0], false);
        dma_channel_set_read_addr(data_chan_slow, &DAC_data[0], false);
        // Re-enable all 4 DMA channels associated with this DAC...
        hw_set_bits(&dma_hw->ch[data_chan_fast].al1_ctrl, DMA_CH0_CTRL_TRIG_EN_BITS);
        hw_set_bits(&dma_hw->ch[data_chan_slow].al1_ctrl, DMA_CH0_CTRL_TRIG_EN_BITS);
        hw_set_bits(&dma_hw->ch[ctrl_chan_fast].al1_ctrl, DMA_CH0_CTRL_TRIG_EN_BITS);
        hw_set_bits(&dma_hw->ch[ctrl_chan_slow].al1_ctrl, DMA_CH0_CTRL_TRIG_EN_BITS);
    }
    void SetFunct (int _value) { Funct = _value; }                        // Function    (Sine/Triangl/Square)
    void SetDutyC (int _value) { DutyC = _value; }                        // Duty cycle  (0->100%)
    void SetRange (int _value) { Range = _value;                          // Range       (Hz/KHz)
                                 DACspeed(Freq * Range); }                // Update State MAchine run speed
    void SetFreq  (int _value) { Freq  = _value;                          // Frequency   (numeric)
                                 DACspeed(Freq * Range); }                // Update State machine run speed    
    void SetPhase (int _value) { Phase = _value;                          // Phase shift (0->360 degrees)
                                 DACspeed(Freq * Range); }
    void DACspeed (int _frequency) {
        // If DAC_div exceeds 2^16 (65,536), the registers wrap around, and the State Machine clock will be incorrect.
        // A slow version of the DAC State Machine is used for frequencies below 17Hz, allowing the value of DAC_div to
        // be kept within range.
        float DAC_freq = _frequency * BitMapSize;                               // Target frequency...
        float DAC_div = 2 * (float)clock_get_hz(clk_sys) / DAC_freq;            // ...calculate the PIO clock divider required for the given Target frequency
        float Fout = 2 * (float)clock_get_hz(clk_sys) / (BitMapSize * DAC_div); // Actual output frequency
         if (_frequency >= 34) {                                                // Fast DAC ( Frequency range from 34Hz to 999Khz )
            pio_sm_set_clkdiv(pio, StateMachine[Fast], DAC_div);                // Set the State Machine clock speed
            pio_sm_set_enabled(pio, StateMachine[Fast], true);                  // Fast State Machine active
            pio_sm_set_enabled(pio, StateMachine[Slow], false);                 // Slow State Machine inactive
        } else {                                                                // Slow DAC ( 1Hz=>16Hz )
            DAC_div = DAC_div / 64;                                             // Adjust DAC_div to keep within useable range
            DAC_freq = DAC_freq * 64;
            pio_sm_set_clkdiv(pio, StateMachine[Slow], DAC_div);                // Set the State Machine clock speed
            pio_sm_set_enabled(pio, StateMachine[Fast], false);                 // Fast State Machine inactive
            pio_sm_set_enabled(pio, StateMachine[Slow], true);                  // Slow State Machine active
        }
    }

    void DataCalc () {
    //    int i,h_index, v_offset = BitMapSize/2 - 1;                                                 // Shift sine waves up above X axis
        int i,j, v_offset = 256/2 - 1;                                                                // Shift sine waves up above X axis
        int _phase;
        const float _2Pi = 6.283;                                                                     // 2*Pi
        float a,b,x1,x2,g1,g2;

    // Scale the phase shift to match data size...    
        _phase = Phase * BitMapSize / 360 ;                                                            // Input  range: 0 -> 360 (degrees)
                                                                                                      // Output range: 0 -> 255 (bytes)
        switch (Funct) {
            case _Sine_:
                DutyC = DutyC % 10;                                                                   // Sine value cycles after 7
                for (i=0; i<BitMapSize; i++) {
    // Add the phase offset and wrap data beyond buffer end back to the buffer start...
                    j = ( i + _phase ) % BitMapSize;                                                  // Horizontal index
                    a = v_offset * sin((float)_2Pi*i / (float)BitMapSize);                            // Fundamental frequency...
                    if (DutyC >= 1) { a += v_offset/3  * sin((float)_2Pi*3*i  / (float)BitMapSize); } // Add  3rd harmonic
                    if (DutyC >= 2) { a += v_offset/5  * sin((float)_2Pi*5*i  / (float)BitMapSize); } // Add  5th harmonic
                    if (DutyC >= 3) { a += v_offset/7  * sin((float)_2Pi*7*i  / (float)BitMapSize); } // Add  7th harmonic
                    if (DutyC >= 4) { a += v_offset/9  * sin((float)_2Pi*9*i  / (float)BitMapSize); } // Add  9th harmonic
                    if (DutyC >= 5) { a += v_offset/11 * sin((float)_2Pi*11*i / (float)BitMapSize); } // Add 11th harmonic
                    if (DutyC >= 6) { a += v_offset/13 * sin((float)_2Pi*13*i / (float)BitMapSize); } // Add 13th harmonic
                    if (DutyC >= 7) { a += v_offset/15 * sin((float)_2Pi*15*i / (float)BitMapSize); } // Add 15th harmonic
                    if (DutyC >= 8) { a += v_offset/17 * sin((float)_2Pi*17*i / (float)BitMapSize); } // Add 17th harmonic
                    if (DutyC >= 9) { a += v_offset/19 * sin((float)_2Pi*19*i / (float)BitMapSize); } // Add 19th harmonic
                    DAC_data[j] = (int)(a)+v_offset;                                                  // Sum all harmonics and add vertical offset
                }
                break;
            case _Square_: 
                b = DutyC * BitMapSize / 100;                                                         // Convert % to value
                for (i=0; i<BitMapSize; i++) {
                    j = ( i + _phase ) % BitMapSize;                                                  // Horizontal index
                    if (b <= i) { DAC_data[j] = 0;   }                                                // First section low
                    else        { DAC_data[j] = 255; }                                                // Second section high
                }
                break;
            case _Triangle_: 
                x1 = (DutyC * BitMapSize / 100) -1;                                                   // Number of data points to peak
                x2 = BitMapSize - x1;                                                                 // Number of data points after peak
                g1 = (BitMapSize - 1) / x1;                                                           // Rising gradient (Max val = BitMapSize -1)
                g2 = (BitMapSize - 1) / x2;                                                           // Falling gradient (Max val = BitMapSize -1)
                for (i=0; i<BitMapSize; i++) {
                    j = ( i + _phase ) % BitMapSize;                                                  // Horizontal index
                    if (i <= x1) { DAC_data[j] = i * g1; }                                            // Rising  section of waveform...
                    if (i > x1)  { DAC_data[j] = (BitMapSize - 1) - ((i - x1) * g2); }                // Falling section of waveform
                }
        }
    }
    // Getter functions...
    int Get_Resource (int _index) {
        int result;
        switch (_index) {
            case _GPIO_:          result = GPIO;              break;
            case _PIO_:           result = _pioNum;           break;
            case _BM_start_:      result = (int)&DAC_data[0]; break;
            case _SM_fast_:       result = SM_fast;           break;
            case _SM_slow_:       result = SM_slow;           break;
            case _SM_code_fast_ : result = SM_code_fast;      break;
            case _SM_code_slow_ : result = SM_code_slow;      break;
            case _DMA_ctrl_fast_: result = ctrl_chan_fast;    break;
            case _DMA_ctrl_slow_: result = ctrl_chan_slow;    break;
            case _DMA_data_fast_: result = data_chan_fast;    break;
            case _DMA_data_slow_: result = data_chan_slow;    break;
            case _Funct_:         result = Funct;             break;
            case _Phase_:         result = Phase;             break;
            case _Freq_:          result = Freq;              break;
            case _Range_:         result = Range;             break;
            case _DutyC_:         result = DutyC;             break;
        }
    return (result);
    }

public:
    // Constructor
    //    Parameters...
    //       _pio = the required PIO channel
    //       _GPIO = the port connecting to the MSB of the R-2-R resistor network.
    // The PIO clock dividers are 16-bit integer, 8-bit fractional, with first-order delta-sigma for the fractional divider.
    // The clock divisor can vary between 1 and 65536, in increments of 1/256.
    // If DAC_div exceeds 2^16 (65,536), the registers wrap around, and the State Machine clock will be incorrect.
    // A slow version of the DAC State Machine is used for frequencies below 17Hz, allowing the value of DAC_div to
    // be kept within range.
        void NewDMAtoDAC_channel(PIO _pio, uint _GPIO) {
            pio = _pio, GPIO = _GPIO;                                               // copy parameters to class vars
            _pioNum = pio_get_index(_pio);
            StateMachine[Fast] = Single_DMA_FIFO_SM_GPIO_DAC(_pio,Fast,_GPIO);      // Create the Fast DAC channel (frequencies: 17Hz to 999KHz)
            StateMachine[Slow] = Single_DMA_FIFO_SM_GPIO_DAC(_pio,Slow,_GPIO);      // Create the Slow DAC channel (frequencies: 0Hz to 16Hz)
        };

public:
    int Single_DMA_FIFO_SM_GPIO_DAC(PIO _pio, int _speed, uint _startpin) {
    // Create a DMA channel and its associated State Machine.
    // DMA => FIFO => State Machine => GPIO pins => DAC
        uint _pioNum = pio_get_index(_pio);                                     // Get user friendly index number.
        int _offset;
        uint _StateMachine = pio_claim_unused_sm(_pio, true);                    // Find a free state machine on the specified PIO - error if there are none.
        uint ctrl_chan = dma_claim_unused_channel(true);                        // Find 2 x free DMA channels for the DAC (12 available)
        uint data_chan = dma_claim_unused_channel(true);

        if (_speed == 1) {
        // Configure the state machine to run the FastDAC program...
            SM_fast = _StateMachine;
            _offset = pio_add_program(_pio, &pio_FastDAC_program);
            SM_code_fast = _offset;
            pio_FastDAC_program_init(_pio, _StateMachine, _offset, _startpin);
            ctrl_chan_fast = ctrl_chan ;                                        // Make details available to getter functions
            data_chan_fast = data_chan ;
        } else {
        // Configure the state machine to run the SlowDAC program...
            SM_slow = _StateMachine;
            _offset = pio_add_program(_pio, &pio_SlowDAC_program);              // Use helper function included in the .pio file.
            SM_code_slow = _offset;
            pio_SlowDAC_program_init(_pio, _StateMachine, _offset, _startpin);
            ctrl_chan_slow = ctrl_chan ;                                        // Make details available to getter functions
            data_chan_slow = data_chan ;
        }

        //  Setup the DAC control channel...
        //  The control channel transfers two words into the data channel's control registers, then halts. The write address wraps on a two-word
        //  (eight-byte) boundary, so that the control channel writes the same two registers when it is next triggered.
        dma_channel_config fc = dma_channel_get_default_config(ctrl_chan);      // default configs
        channel_config_set_transfer_data_size(&fc, DMA_SIZE_32);                // 32-bit txfers
        channel_config_set_read_increment(&fc, false);                          // no read incrementing
        channel_config_set_write_increment(&fc, false);                         // no write incrementing
        dma_channel_configure(
            ctrl_chan,
            &fc,
            &dma_hw->ch[data_chan].al1_transfer_count_trig,                     // txfer to transfer count trigger
            &transfer_count,
            1,
            false
        );
        //  Setup the DAC data channel...
        //  32 bit transfers. Read address increments after each transfer.
        fc = dma_channel_get_default_config(data_chan);
        channel_config_set_transfer_data_size(&fc, DMA_SIZE_32);                // 32-bit txfers
        channel_config_set_read_increment(&fc, true);                           // increment the read adddress
        channel_config_set_write_increment(&fc, false);                         // don't increment write address
        channel_config_set_dreq(&fc, pio_get_dreq(_pio, _StateMachine, true));  // Transfer when PIO SM TX FIFO has space
        channel_config_set_chain_to(&fc, ctrl_chan);                            // chain to the controller DMA channel
        channel_config_set_ring(&fc, false, 9);                                 // 8 bit DAC 1<<9 byte boundary on read ptr. This is why we needed alignment!
        dma_channel_configure(
            data_chan,                                                          // Channel to be configured
            &fc,                                                                // The configuration we just created
            &_pio->txf[_StateMachine],                                          // Write to FIFO
            DAC_data,                                                           // The initial read address (AT NATURAL ALIGNMENT POINT)
            BitMapSize,                                                         // Number of transfers; in this case each is 2 byte.
            false                                                               // Don't start immediately. All 4 control channels need to start simultaneously
                                                                                // to ensure the correct phase shift is applied.
        );
        // Note: All DMA channels are left running permanently. The active channel is selected by enabling/disabling the associated State Machine.
        DAC_channel_mask += (1u << ctrl_chan) ;                                 // Save details of DMA control channel to global variable

        return(_StateMachine);
    }
};

class blink_forever {                                                      // Class to initialise a state machine to blink a GPIO pin
PIO pio ;                                                                   // Class wide variables to share value with setter function
uint pioNum, StateMachine, Freq, _offset ;
public:
    blink_forever(PIO _pio) {
        pio = _pio;                                                        // transfer parameter to class wide var
        pioNum = pio_get_index(_pio);
        StateMachine = pio_claim_unused_sm(_pio, true);                    // Find a free state machine on the specified PIO - error if there are none.
        _offset = pio_add_program(_pio, &pio_blink_program);
        blink_program_init(_pio, StateMachine, _offset, LED );
        pio_sm_set_enabled(_pio, StateMachine, true);
    }

    // Setter function...
    void Set_Frequency(int _frequency){
        Freq = _frequency;                                                  // Copy parm to class var
    // Frequency scaled by 2000 as blink.pio requires this number of cycles to complete...
        float DAC_div = (float)clock_get_hz(clk_sys) /((float)_frequency*2000);
        pio_sm_set_clkdiv(pio, StateMachine, DAC_div);                      // Set the State Machine clock speed
    }

    // Getter function...
    int Get_Resource (int _index) {
        int result;
        switch (_index) {
            case _GPIO_:          result = LED;               break;
            case _SM_:            result = StateMachine;      break;
            case _PIO_:           result = pioNum;            break;
            case _Freq_:          result = Freq;              break;
        }
    return (result);
    }
};

void ChanInfo ( DACchannel DACchannel[], int _chanNum) {
// Print current channel parameters to the console...
    char Chan, WaveStr[9], MultStr[4];
    int value = DACchannel[_chanNum].Get_Resource(_Funct_);

    int test = DACchannel[_chanNum].Get_Resource(_Phase_);

    switch ( value ) {
        case _Sine_:     strcpy(WaveStr, "Sine");     break;
        case _Triangle_: strcpy(WaveStr, "Triangle"); break;
        case _Square_:   strcpy(WaveStr,"Square");
    }
    _chanNum == 0 ? Chan = 'A' : Chan = 'B';
    DACchannel[_chanNum].Get_Resource(_Range_) == 1 ? strcpy(MultStr,"Hz ") : strcpy(MultStr,"KHz");
    printf("\tChannel %c: Freq:%03d%s Phase:%03d  Wave:%s\n", Chan, DACchannel[_chanNum].Get_Resource(_Freq_),
        MultStr, DACchannel[_chanNum].Get_Resource(_Phase_), WaveStr);
}

void SysInfo ( DACchannel DACchannel[], blink_forever LED_blinky) {
// Print system and resource allocation details...
    int a,b,c,d ;
    a = LED_blinky.Get_Resource(_PIO_);
    b = LED_blinky.Get_Resource(_SM_);
    c = LED_blinky.Get_Resource(_GPIO_);
    d = LED_blinky.Get_Resource(_Freq_);
    printf("\n|-----------------------------------------------------------|\n");
    printf("| Waveform Generator Ver: 0.0.1       Date: 21/03/2013      |\n");
    printf("|-----------------------------|-----------------------------|\n");
    printf("| LED blinker                 |                             |\n");
    printf("|-----------------------------|                             |\n");
    printf("|   PIO:          %2d          |  Key:                       |\n",a);
    printf("|   SM:           %2d          |   SM = State machine        |\n",b);
    printf("|   GPIO:         %2d          |   BM = Bitmap               |\n",c);
    printf("|   Frequency:    %2dHz        |                             |\n",d);
    printf("|-----------------------------|-----------------------------|\n");
    printf("| DAC channel A               | DAC channel B               |\n");
    printf("|-----------------------------|-----------------------------|\n");
    a = DACchannel[_A].Get_Resource(_PIO_);
    b = DACchannel[_B].Get_Resource(_PIO_);
    printf("| PIO:             %d          | PIO:             %d          |\n",a,b);
    a = DACchannel[_A].Get_Resource(_GPIO_);
    b = DACchannel[_B].Get_Resource(_GPIO_);
    printf("| GPIO:          %d-%d          | GPIO:         %d-%d          |\n",a,a+7,b,b+7);
    printf("| BM size:  %8d          | BM size:  %8d          |\n", BitMapSize,  BitMapSize);
    a = DACchannel[_A].Get_Resource(_BM_start_);
    b = DACchannel[_B].Get_Resource(_BM_start_);
    printf("| BM start: %x          | BM start: %x          |\n",a,b);
    printf("| Divider:     %05x          | Divider:     %05x          |\n",0,0);
    printf("|--------------|--------------|--------------|--------------|\n");
    printf("| Fast DAC     | Slow DAC     | Fast DAC     |  Slow DAC    |\n");
    printf("|--------------|--------------|--------------|--------------|\n");
    a = DACchannel[_A].Get_Resource(_SM_fast_);
    b = DACchannel[_A].Get_Resource(_SM_slow_);
    c = DACchannel[_B].Get_Resource(_SM_fast_);
    d = DACchannel[_B].Get_Resource(_SM_slow_);
    printf("| SM:        %d | SM:        %d | SM:        %d | SM:        %d |\n",a,b,c,d);
    a = DACchannel[_A].Get_Resource(_SM_code_fast_);
    b = DACchannel[_A].Get_Resource(_SM_code_slow_);
    c = DACchannel[_B].Get_Resource(_SM_code_fast_);
    d = DACchannel[_B].Get_Resource(_SM_code_slow_);
    printf("| SM code:  %2d | SM code:  %2d | SM code:  %2d | SM code:  %2d |\n",a,b,c,d);
    a = DACchannel[_A].Get_Resource(_DMA_ctrl_fast_);
    b = DACchannel[_A].Get_Resource(_DMA_ctrl_slow_);
    c = DACchannel[_B].Get_Resource(_DMA_ctrl_fast_);
    d = DACchannel[_B].Get_Resource(_DMA_ctrl_slow_);
    printf("| DMA ctrl: %2d | DMA ctrl: %2d | DMA ctrl: %2d | DMA ctrl: %2d |\n",a,b,c,d);
    a = DACchannel[_A].Get_Resource(_DMA_data_fast_);
    b = DACchannel[_A].Get_Resource(_DMA_data_slow_);
    c = DACchannel[_B].Get_Resource(_DMA_data_fast_);
    d = DACchannel[_B].Get_Resource(_DMA_data_slow_);
    printf("| DMA data: %2d | DMA data: %2d | DMA data: %2d | DMA data: %2d |\n",a,b,c,d); 
    printf("|--------------|--------------|--------------|--------------|\n");
}

static inline void cs_select() {
    asm volatile("nop \n nop \n nop");
    gpio_put(Nixie_CS, 0);  // Active low
    asm volatile("nop \n nop \n nop");
}

static inline void cs_deselect() {
    asm volatile("nop \n nop \n nop");
    gpio_put(Nixie_CS, 1);
    asm volatile("nop \n nop \n nop");
}

static void SPI_Nixie_Write(int _data) {
    uint8_t buff[2];
    buff[0] = _data / 256;                                                      // MSB data
    buff[1] = _data % 256;                                                      // LSB data
    cs_select();
    spi_write_blocking(SPI_PORT, buff, 2);
    cs_deselect();
}

static char * getLine(bool fullDuplex = false, char lineBreak = '\n') {
/*
 *  read a line of any  length from stdio (grows)
 *
 *  @param fullDuplex input will echo on entry (terminal mode) when false
 *  @param linebreak defaults to "\n", but "\r" may be needed for terminals
 *  @return entered line on heap - don't forget calling free() to get memory back
 */
    // th line buffer
    // will allocated by pico_malloc module if <cstdlib> gets included
    char * pStart = (char*)malloc(startLineLength); 
    char * pPos = pStart;  // next character position
    size_t maxLen = startLineLength; // current max buffer size
    size_t len = maxLen; // current max length
    int c;

    if(!pStart) {
        return NULL; // out of memory or dysfunctional heap
    }

    while(1) {
        c = getchar(); // expect next character entry
        if(c == eof || c == lineBreak) {
            break;     // non blocking exit
        }
         if (fullDuplex) {
            putchar(c); // echo for fullDuplex terminals
        }
        if(--len == 0) { // allow larger buffer
            len = maxLen;
            // double the current line buffer size
            char *pNew  = (char*)realloc(pStart, maxLen *= 2);
            if(!pNew) {
                free(pStart);
                return NULL; // out of memory abort
            }
            // fix pointer for new buffer
            pPos = pNew + (pPos - pStart);
            pStart = pNew;
        }
        // stop reading if lineBreak character entered 
        if((*pPos++ = c) == lineBreak) {
            break;
        }
    }
    *pPos = '\0';   // set string end mark
    return pStart;
}

int main() {
    stdio_init_all();

// Set SPI0 at 0.5MHz.
    spi_init(SPI_PORT, 500 * 1000);
    gpio_set_function(PIN_CLK, GPIO_FUNC_SPI);
    gpio_set_function(PIN_TX, GPIO_FUNC_SPI);

// Chip select is active-low, so initialise to a driven-high state...
    gpio_init(Nixie_CS);
    gpio_set_dir(Nixie_CS, GPIO_OUT);
    gpio_put(Nixie_CS, 1);

// Initialise remaining SPI connections...
    gpio_set_dir(PIN_CLK, GPIO_OUT);
    gpio_set_dir(PIN_TX, GPIO_OUT);

    DACchannel DACchannel[2];                                                // Array to hold the two DAC channel objects

// Set up the objects controlling the various State Machines...
// Note: Both DAC channels need to be on the same PIO to acheive accurate phase sync.
    DACchannel[_A].NewDMAtoDAC_channel(pio1,0);                              // First  DAC channel object in array - resistor network connected to GPIO0->7
    DACchannel[_B].NewDMAtoDAC_channel(pio1,8);                              // Second DAC channel object in array - resistor network connected to GPIO8->15
    blink_forever LED_blinky(pio0);                                          // Onboard LED blinky object

// Set LED to slow flash indicates waiting for USB connection...
    LED_blinky.Set_Frequency(1);                                             // 1Hz

// Wait for USB connection...
    while (!stdio_usb_connected()) { sleep_ms(100); }

// USB connection established, set LED to rapid flash...
    LED_blinky.Set_Frequency(10);                                             // 10Hz

    SysInfo(DACchannel, LED_blinky);                                         // Show configuration (optional)
//  printf(HelpText);                                                        // Show instructions  (optional)

// Set default run time settings...
    DACchannel[_A].SetFreq(100),        DACchannel[_B].SetFreq(100) ;        // 100
    DACchannel[_A].SetRange(1),         DACchannel[_B].SetRange(1) ;         // Hz
    DACchannel[_A].SetPhase(0),         DACchannel[_B].SetPhase(180) ;       // 180 phase diff
    DACchannel[_A].SetFunct(_Sine_),    DACchannel[_B].SetFunct(_Sine_) ;    // Sine wave, no harmonics
    DACchannel[_A].SetDutyC(50),        DACchannel[_B].SetDutyC(50);         // 50% Duty cycle
    DACchannel[_A].DataCalc(),          DACchannel[_B].DataCalc();           // Generate the two data sets

    SPI_Nixie_Write(DACchannel[_A].Get_Resource(_Freq_));                    // Frequency => Nixie display

// Starting all 4 DMA channels simultaneously ensures phase sync across all State Machines...
    dma_start_channel_mask(DAC_channel_mask);

    while(1) {
        char *inString = getLine(true, '\r') ;
        ParmCnt = 0, Parm[0]=0,  Parm[1]=0,  Parm[2]=0,  Parm[3]=0; 

        // Perform single character instructions...
        if (inString[0] == '?') { printf(HelpText);                }            // Help text
        if (inString[0] == 'S') { ChanInfo(DACchannel, _A);                     // Status info
                                  ChanInfo(DACchannel, _B);        }
        if (inString[0] == 'I') { SysInfo(DACchannel, LED_blinky); }

        // Select DAC channel A or B...
        if (inString[0] == 'A') { SelectedChan = 0b0001;           }            // Channel A
        if (inString[0] == 'B') { SelectedChan = 0b0010;           }            // Channel B
        if (inString[0] == 'C') { SelectedChan = 0b0011;           }            // Channel A & B
        // Parse command line to extract numeric parameters. Leading zeros are ignored...
        i = 1 ;                                                                 // Skip chars 0 & 1
        while (i++ < strlen(inString)-1 ) {                                     // Start at char 2
            if ( inString[i] == ',' ) { ParmCnt++ ; }                           // Next parameter
            else                      { Parm[ParmCnt] *= 10;                    // Next digit. Bump the existing decimal digits
                                        Parm[ParmCnt] += inString[i] - '0'; }   // Convert character to integer and add
        }
        // Perform the selected command...
        switch ( inString[1] ) {
            case 'w':                                           // Frequency sweep
                i = Parm[0];
                for (;;) {
                    DACchannel[_A].ReInit();                    // Stop DAC channel A and re-initialise DMA to start of Bitmap data
                    DACchannel[_B].ReInit();                    // Stop DAC channel B and re-initialise DMA to start of Bitmap data
                    if (SelectedChan & 0b01) {
                        DACchannel[_A].SetFreq(i); 
                        ChanInfo(DACchannel, _A);               // Update the terminal
                    }
                    if (SelectedChan & 0b10) {
                        DACchannel[_B].SetFreq(i);
                        ChanInfo(DACchannel, _B);               // Update the terminal
                        }
                    dma_start_channel_mask(DAC_channel_mask);   // Atomically Restart all 4 DMA channels...
                    SPI_Nixie_Write(i);                         // Update Nixie display
                    if (i==Parm[0]) { dirn = 1;
                                      sleep_ms(Parm[3]); }      // Count up from zero, pause at end
                    if (i>=Parm[1]) { dirn =-1; 
                                      sleep_ms(Parm[3]); }      // Count down from 100, pause at start
                    i = i + dirn;
                    c = getchar_timeout_us (0);                 // Non-blocking char input
                    if ((c>=32) & (c<=126)) { break; }          // exit on keypress
                    sleep_ms(Parm[2]);                          // Speed of scan
                }
                break;
            case 's':                                           // Sine wave
                if (SelectedChan & 0b01) {
                    DACchannel[_A].SetFunct(_Sine_);
                    DACchannel[_A].SetDutyC(Parm[0]);
                    DACchannel[_A].DataCalc();
                }
                if (SelectedChan & 0b10) {
                    DACchannel[_B].SetFunct(_Sine_);
                    DACchannel[_B].SetDutyC(Parm[0]);
                    DACchannel[_B].DataCalc();
                }
                break;
            case 't':                                           // Triangle wave
                if ( Parm[0] > 100 ) { Parm[0] = 100; }         // Hard limit @ 100%
                if (SelectedChan & 0b01) {
                    DACchannel[_A].SetFunct(_Triangle_);
                    DACchannel[_A].SetDutyC(Parm[0]);
                    DACchannel[_A].DataCalc();
                }
                if (SelectedChan & 0b10) {
                    DACchannel[_B].SetFunct(_Triangle_);
                    DACchannel[_B].SetDutyC(Parm[0]);
                    DACchannel[_B].DataCalc();
                }
                break;
            case 'q':
                if ( Parm[0] > 100 ) { Parm[0] = 100; }         // Hard limit @ 100%
                if (SelectedChan & 0b01) {
                    DACchannel[_A].SetFunct(_Square_);
                    DACchannel[_A].SetDutyC(Parm[0]);
                    DACchannel[_A].DataCalc();
                }
                if (SelectedChan & 0b10) {
                    DACchannel[_B].SetFunct(_Square_);
                    DACchannel[_B].SetDutyC(Parm[0]);
                    DACchannel[_B].DataCalc();
                }
                break;
            case 'h':                                           // Set Hz
                if (SelectedChan & 0b01) { DACchannel[_A].SetRange(1); }
                if (SelectedChan & 0b10) { DACchannel[_B].SetRange(1); }
                break;
            case 'k':                                           // Set KHz
                if (SelectedChan & 0b01) { DACchannel[_A].SetRange(1000); }
                if (SelectedChan & 0b10) { DACchannel[_B].SetRange(1000); }
                break;
            case 'f':
                DACchannel[_A].ReInit();                        // Stop DAC channel A and re-initialise DMA to start of Bitmap data
                DACchannel[_B].ReInit();                        // Stop DAC channel B and re-initialise DMA to start of Bitmap data
                // TBD: this may throw any existing phase setting out.
                // Recalc both channels ensures phase settings are preserved.
                if (SelectedChan & 0b01) { DACchannel[_A].SetFreq(Parm[0]); }
                if (SelectedChan & 0b10) { DACchannel[_B].SetFreq(Parm[0]); }
                dma_start_channel_mask(DAC_channel_mask);       // Atomically Restart all 4 DMA channels
                break;
            case 'p':
                DACchannel[_A].ReInit();                        // Stop DAC channel A and re-initialise DMA to start of Bitmap data
                DACchannel[_B].ReInit();                        // Stop DAC channel B and re-initialise DMA to start of Bitmap data
                if (SelectedChan & 0b01) {
                    DACchannel[_A].SetPhase(Parm[0]);           // Update DAC phase.
                    DACchannel[_A].DataCalc();                  // Update Bitmap data to include new DAC phase
                }
                if (SelectedChan & 0b10) {
                    DACchannel[_B].SetPhase(Parm[0]);           // Update DAC phase.
                    DACchannel[_B].DataCalc();                  // Update Bitmap data to include new DAC phase
                }
                dma_start_channel_mask(DAC_channel_mask);       // Atomically Restart all 4 DMA channels
                break;
            default:
                printf("\tUnknown command\n");
        }
        if (SelectedChan & 0b01) { ChanInfo(DACchannel, _A); }   // Update the terminal
        if (SelectedChan & 0b10) { ChanInfo(DACchannel, _B); }
        SPI_Nixie_Write(Parm[0]);                                // Update Nixie display
        free(inString);                                          // free buffer
    }
    return 0;
}