u2f-zero/firmware/src/Interrupts.c

/*
 * Copyright (c) 2016, Conor Patrick
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include <SI_EFM8UB1_Register_Enums.h>
#include <stdint.h>
#include "app.h"
#include "i2c.h"

#include "bsp.h"

// millisecond timer
uint32_t data _MS_ = 0;
SI_INTERRUPT (TIMER2_ISR, TIMER2_IRQn)
{
	TMR2CN0_TF2H = 0;
	++_MS_;
}

#define SMB_STATUS_START			0xE0
#define SMB_STATUS_MTX				0xC0
#define SMB_STATUS_MRX				0x80
#define SMB_STATE_MASK				0xF0


#define SMB_TX_STATE_MASK (SMB_WRITE_EXT|SMB_WRITE)
#define SMB_TX_EXT (SMB_WRITE|SMB_WRITE_EXT)
#define SMB_TX (SMB_WRITE)

data uint8_t SMB_addr 				= 0;
uint8_t * SMB_write_buf 			= NULL;
data uint8_t SMB_write_len 			= 0;
data uint8_t SMB_write_offset 		= 0;
data uint8_t SMB_read_len 			= 0;
data uint8_t SMB_read_offset 		= 0;
uint8_t * SMB_read_buf 				= NULL;
uint8_t * SMB_write_ext_buf 		= NULL;
data uint8_t  SMB_write_ext_len 	= 0;
data uint8_t  SMB_write_ext_offset 	= 0;
uint8_t SMB_preflags 				= 0;
uint16_t  SMB_crc 					= 0;
data uint8_t  SMB_crc_offset 		= 0;
data volatile uint8_t SMB_FLAGS 	= 0;

static void update_from_packet_length()
{
	if (SMB_read_buf[0] <= SMB_read_len)
	{
		SMB_read_len = SMB_read_buf[0];
	}
	else
	{
		// truncated read
		SMB_FLAGS |= SMB_READ_TRUNC;
	}
}

static void _feed_crc(uint8_t b)
{
	SMB_crc = feed_crc(SMB_crc,b);
}

static void restart_bus()
{
	SMB0CF &= ~0x80;
	SMB0CF |= 0x80;
	SMB0CN0_STA = 0;
	SMB0CN0_STO = 0;
	SMB0CN0_ACK = 0;
	SMB_BUSY_CLEAR();
}

SI_INTERRUPT (SMBUS0_ISR, SMBUS0_IRQn)
{
	data uint8_t bus = SMB0CN0 & SMB_STATE_MASK;
	data uint8_t c;
	if (SMB0CN0_ARBLOST != 0)
	{
		goto fail;
	}

	switch (bus)
	{
		case SMB_STATUS_START:
			SMB0DAT = SMB_addr | (SMB_FLAGS & SMB_READ);
			SMB0CN0_STA = 0;
			break;

		case SMB_STATUS_MTX:
			if (!SMB0CN0_ACK)
			{
				// NACK
				// end transaction
				SMB0CN0_STO = 1;
				SMB_FLAGS |= SMB_RECV_NACK;
				SMB_BUSY_CLEAR();
			}
			else if (!SMB_WRITING())
			{
				// do nothing and switch to receive mode
			}
			else if (SMB_write_offset < SMB_write_len)
			{
				// start writing first buffer
				// dont crc first byte for atecc508a
				c = SMB_write_buf[SMB_write_offset++];
				if (SMB_write_offset > 1) _feed_crc(c);
				SMB0DAT = c;

			}
			else if(SMB_WRITING_EXT() && SMB_write_ext_offset < SMB_write_ext_len)
			{
				// start writing second optional buffer
				c = SMB_write_ext_buf[SMB_write_ext_offset++];
				_feed_crc(c);
				SMB0DAT = c;
			}
			else
			{
				// write optional CRC
				switch(SMB_crc_offset++)
				{
					case 0:
						SMB_crc = reverse_bits(SMB_crc);
						SMB0DAT = (uint8_t)SMB_crc;
						break;
					case 1:
						SMB0DAT = (uint8_t)(SMB_crc>>8);
						break;
					case 2:
						SMB0CN0_STO = 1;
						SMB_BUSY_CLEAR();
				}
			}

			break;

		case SMB_STATUS_MRX:
			// read in buffer

			if (SMB_read_offset < SMB_read_len)
			{
				c = SMB0DAT;
				SMB_read_buf[SMB_read_offset] = c;

				// update with length from packet
				// warning this is device specific to atecc508a
				if (SMB_read_offset == 0)
				{
					update_from_packet_length();
				}

				if ((SMB_read_offset < (SMB_read_len - 2)))
				{
					SMB_crc = feed_crc(SMB_crc, c);
				}

				SMB_read_offset++;
				SMB0CN0_ACK = 1;
			}
			else
			{
				// end transaction

				SMB_crc = reverse_bits(SMB_crc);
				SMB_BUSY_CLEAR();
				SMB0CN0_ACK = 0;
				SMB0CN0_STO = 1;
			}

			break;

		default:
			goto fail;
			break;

	}


	// interrupt flag
	SMB0CN0_SI = 0;
	return;

	fail:
		u2f_printb("smbus fail ",1,bus);
		//restart_bus();
		SMB0CN0_SI = 0;
}


// A Timer3 interrupt indicates an SMBus SCL low timeout.
// The SMBus is disabled and re-enabled here
SI_INTERRUPT (TIMER3_ISR, TIMER3_IRQn)
{
	//restart_bus();
}