Add preliminary arduino firmware code

firmware/README.md

@@ -0,0 +1,12 @@
+Firmware
+========
+The kiln controller circuit communicates with the raspberry pi using an I2C bus. This allows multiple connectors to be stacked to enable more controllers and feedback circuits.
+
+Communication protocol
+----------------------
+
+| Register	|	Input 		| Meaning						|
+-------------------------------------------------------------
+| ord('I')	|   True/False	| Toggle ignition				|
+| ord('M')  |	integer		| Move motor 					|
+| ord('F')	|	None		| Show flame status				|

firmware/controller/controller.ino

@@ -0,0 +1,177 @@
+#include <Bounce2.h>
+
+#define PIN_IGNITE    10
+#define PIN_STEP1     9
+#define PIN_STEP2     8
+#define PIN_STEP3     7
+#define PIN_STEP4     6
+#define PIN_AUXTEMP   A1
+#define PIN_TEMP_CS   4
+#define PIN_LOADCELL  A3
+#define PIN_FLAME_A   A2
+#define PIN_FLAME_D   1
+#define PIN_REGLIMIT  5
+
+#define STEP_SPEED 250//in steps per second
+#define TEMP_UPDATE 100 //milliseconds
+#define MOTOR_TIMEOUT 5000 //milliseconds
+
+#include <Stepper.h>
+#include <Wire.h>
+#include <SPI.h>
+#include <Adafruit_MAX31855.h>
+
+struct Status {
+  unsigned char ignite;
+  unsigned char flame;
+  unsigned int motor;
+  float main_temp;
+  float ambient;
+  float weight;
+  float aux_temp[2];
+} status;
+uint8_t* status_data = (uint8_t*) &status;
+
+const float step_interval = 1. / STEP_SPEED * 1000.; //milliseconds
+
+//intermediate variables
+Adafruit_MAX31855 thermo(PIN_TEMP_CS);
+Stepper stepper(2048, PIN_STEP1, PIN_STEP3, PIN_STEP2, PIN_STEP4);
+Bounce debouncer = Bounce();
+
+unsigned int n_clicks = 0; //Number of full rotations
+unsigned long stepper_target;
+char i2c_command;
+float next_step;
+unsigned long next_temp;
+unsigned char motor_active = false;
+
+void setup() {
+  status.flame = false;
+  status.weight = 0.;
+  status.aux_temp[0] = 0.;
+  status.aux_temp[1] = 0.;
+  
+  //Setup I2C
+  Wire.begin(0x08);
+  Wire.onRequest(i2c_update);
+  Wire.onReceive(i2c_action);
+  
+  //Set up regulator stepper
+  status.motor = 0;
+  stepper_target = 0;
+  
+  //Set pullup for regulator limit
+  pinMode(PIN_REGLIMIT, INPUT);
+  digitalWrite(PIN_REGLIMIT, HIGH);
+  debouncer.attach(PIN_REGLIMIT);
+  debouncer.interval(5);
+  
+  //setup ignition mosfet
+  pinMode(PIN_IGNITE, OUTPUT);
+  digitalWrite(PIN_IGNITE, LOW);
+  status.ignite = false;
+  
+  //set initial temperature
+  delay(500);
+  update_temp();
+  next_temp = millis() + TEMP_UPDATE;
+}
+
+unsigned long now;
+void loop() {
+  now = millis();
+  
+  if (stepper_target != status.motor && now > next_step) {
+    int dir = status.motor < stepper_target ? 1 : -1;
+    stepper.step(dir);
+    
+    boolean check = debouncer.update() && debouncer.read() == HIGH;
+    if (check) {
+      n_clicks += dir;
+    }
+    
+    //If homing, continuing moving until switch is zero
+    if (stepper_target == 0 && check && n_clicks == 0) {
+      status.motor = 0;
+    } else {
+      status.motor += dir;
+    }
+    
+    next_step += step_interval;
+  }
+  
+  //put motor to sleep after timeout
+  if (motor_active && (now - next_step) > MOTOR_TIMEOUT) {
+    digitalWrite(PIN_STEP1, LOW);
+    digitalWrite(PIN_STEP2, LOW);
+    digitalWrite(PIN_STEP3, LOW);
+    digitalWrite(PIN_STEP4, LOW);
+    motor_active = false;
+  }
+  
+  //update temperature
+  if (now > next_temp) {
+    update_temp();
+    next_temp += TEMP_UPDATE;
+  }
+  
+  //check flame status
+}
+
+void set_regulator(unsigned long pos) {
+  motor_active = true;
+  if (stepper_target == status.motor)
+    next_step = millis(); //Start stepping immediately
+  stepper_target = pos;
+}
+
+void update_temp() {
+  TempData temps;
+  thermo.readAll(temps);
+  status.main_temp = temps.celcius;
+  status.ambient = temps.internal;
+}
+
+void i2c_update() {
+  //update temperatures
+  
+  if (i2c_command == 'M') {
+    Wire.write((byte*) &(status.motor), 4);
+  } else if (i2c_command == 'I') {
+    Wire.write((byte*) &(status.ignite), 1);
+  } else if (i2c_command == 'T') {
+    Wire.write((byte*) &(status.main_temp), 4);
+  } else if (i2c_command == 'F') {
+    Wire.write((byte*) &(status.flame), 1);
+  } else {
+    Wire.write(status_data, sizeof(struct Status));
+  }
+  
+  i2c_command = 0;
+}
+
+byte buffer[32];
+void i2c_action(int nbytes) {
+  i2c_command = Wire.read();
+  
+  int i = 0;
+  while (Wire.available()) {
+    buffer[i++] = Wire.read();
+  }
+  
+  if (nbytes == 1) {
+    return; //Command already stored, no arguments
+  }
+  
+  switch (i2c_command) {
+    case 'M':
+      set_regulator(*((unsigned long*) buffer));
+      break;
+    case 'I':
+      digitalWrite(PIN_TEMP_CS, buffer[0]);
+      break;
+  }
+  
+  i2c_command = 0;
+}

firmware/controller/protocol.cpp

@@ -0,0 +1,39 @@
+#include "protocol.h"
+
+char Comm::buffer[BUFFER_LENGTH+1];
+int Comm::_nacts;
+char Comm::_commands[MAX_ACTIONS];
+char* (*Comm::_actions[MAX_ACTIONS])(int, char*);
+char Comm::_current_cmd;
+int  Comm::_current_len;
+
+Comm::Comm(int addr) {
+  Wire.begin(addr);
+  Wire.onReceive(_handle_request);
+  Wire.onRequest(_handle_response);
+}
+
+int Comm::action(char cmd, char* (*func)(int, char*)) {
+  if (_nacts >= MAX_ACTIONS)
+    return 1;
+    
+  _actions[_nacts] = func;
+  return 0;
+}
+
+void Comm::_handle_request(int nbytes) {
+  _current_cmd = Wire.read();
+  _current_len = nbytes-1;
+  for (int i = 0; i < nbytes-1; i++) {
+    buffer[i] = Wire.read();
+  }
+}
+
+void Comm::_handle_response() {
+  for (int i = 0; i < MAX_ACTIONS; i++) {
+    if (_commands[i] == _current_cmd) {
+      _actions[i](_current_len, buffer);
+    }
+  }
+  Wire.write(buffer);
+}

firmware/controller/protocol.h

@@ -0,0 +1,25 @@
+#ifndef PROTOCOL_H
+#define PROTOCOL_H
+
+#include "Wire.h"
+
+#define MAX_ACTIONS 16
+
+class Comm {
+  private:
+    static char buffer[BUFFER_LENGTH+1];
+    static int _nacts;
+    static char _commands[MAX_ACTIONS];
+    static char* (*_actions[MAX_ACTIONS])(int, char*);
+    static char _current_cmd;
+    static int  _current_len;
+    
+    static void _handle_request(int);
+    static void _handle_response(void);
+  
+  public:
+    Comm(int addr);
+    int action(char, char* (*)(int, char*));
+};
+
+#endif //PROTOCOL_H

kiln/interface.py

@@ -2,10 +2,10 @@ import smbus
 import struct
 from collections import namedtuple
 
-Status = namedtuple('Status', 'ignite flame motor main_temp weight aux_temp0 aux_temp1')
+Status = namedtuple('Status', 'ignite flame motor main_temp ambient weight aux_temp0 aux_temp1')
 
 class Kiln(object):
-    fmt = struct.Struct('<2BI4f')
+    fmt = struct.Struct('<2BH5f')
     def __init__(self, addr, bus=1):
         self.bus = smbus.SMBus(1)
         self.addr = addr