controller/Scan/ISSILed/i2c.c

/*
 * Copyright ( C ) 2014 Jan Rychter
 * Modifications ( C ) 2015 Jacob Alexander
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files ( the "Software" ), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

// ----- Includes ----

// Compiler Includes
#include <Lib/ScanLib.h>

// Project Includes
#include <print.h>

// Local Includes
#include "i2c.h"



// ----- Variables -----

volatile I2C_Channel i2c_channels[1];



// ----- Functions -----

inline void i2c_setup(  )
{
	// Enable I2C internal clock
	SIM_SCGC4 |= SIM_SCGC4_I2C0; // Bus 0

	// External pull-up resistor
	PORTB_PCR0 = PORT_PCR_ODE | PORT_PCR_SRE | PORT_PCR_DSE | PORT_PCR_MUX(2);
	PORTB_PCR1 = PORT_PCR_ODE | PORT_PCR_SRE | PORT_PCR_DSE | PORT_PCR_MUX(2);

	// SCL Frequency Divider
	// 1.8 MBaud ( likely higher than spec )
	// 0x82 -> 36 MHz / (4 * 3) = 2.25 MBaud
	// 0x80 => mul(4)
	// 0x05 => ICL(5)
	I2C0_F = 0x84;
	I2C0_FLT = 4;
	I2C0_C1 = I2C_C1_IICEN;
	I2C0_C2 = I2C_C2_HDRS; // High drive select

	// Enable I2C Interrupt
	NVIC_ENABLE_IRQ(  IRQ_I2C0  );
}

uint8_t i2c_busy()
{
	volatile I2C_Channel *channel = &( i2c_channels[0] );
	if ( channel->status == I2C_BUSY )
	{
		return 1;
	}

	return 0;
}


// These are here for readability and correspond to bit 0 of the address byte.
#define I2C_WRITING 0
#define I2C_READING 1

int32_t i2c_send_sequence(
	uint16_t *sequence,
	uint32_t sequence_length,
	uint8_t *received_data,
	void ( *callback_fn )( void* ),
	void *user_data
) {
	volatile I2C_Channel *channel = &( i2c_channels[0] );
	int32_t result = 0;
	uint8_t status;

	if ( channel->status == I2C_BUSY )
	{
		return -1;
	}

	// Debug
	/*
	for ( uint8_t c = 0; c < sequence_length; c++ )
	{
		printHex( sequence[c] );
		print(" ");
	}
	print(NL);
	*/

	channel->sequence = sequence;
	channel->sequence_end = sequence + sequence_length;
	channel->received_data = received_data;
	channel->status = I2C_BUSY;
	channel->txrx = I2C_WRITING;
	channel->callback_fn = callback_fn;
	channel->user_data = user_data;

	// reads_ahead does not need to be initialized

	// Acknowledge the interrupt request, just in case
	I2C0_S |= I2C_S_IICIF;
	I2C0_C1 = ( I2C_C1_IICEN | I2C_C1_IICIE );

	// Generate a start condition and prepare for transmitting.
	I2C0_C1 |= ( I2C_C1_MST | I2C_C1_TX );

	status = I2C0_S;
	if ( status & I2C_S_ARBL )
	{
		warn_print("Arbitration lost");
		result = -1;
		goto i2c_send_sequence_cleanup;
	}

	// Write the first (address) byte.
	I2C0_D = *channel->sequence++;

	// Everything is OK.
	return result;

i2c_send_sequence_cleanup:
	I2C0_C1 &= ~( I2C_C1_IICIE | I2C_C1_MST | I2C_C1_TX );
	channel->status = I2C_ERROR;
	return result;
}


void i2c0_isr()
{
	volatile I2C_Channel* channel = &i2c_channels[0];
	uint8_t element;
	uint8_t status;

	status = I2C0_S;

	// Acknowledge the interrupt request
	I2C0_S |= I2C_S_IICIF;

	// Arbitration problem
	if ( status & I2C_S_ARBL )
	{
		warn_print("Arbitration error");
		I2C0_S |= I2C_S_ARBL;
		goto i2c_isr_error;
	}

	if ( channel->txrx == I2C_READING )
	{

		switch( channel->reads_ahead )
		{
		// All the reads in the sequence have been processed ( but note that the final data register read still needs to
		// be done below! Now, the next thing is either a restart or the end of a sequence. In any case, we need to
		// switch to TX mode, either to generate a repeated start condition, or to avoid triggering another I2C read
		// when reading the contents of the data register.
		case 0:
			I2C0_C1 |= I2C_C1_TX;

			// Perform the final data register read now that it's safe to do so.
			*channel->received_data++ = I2C0_D;

			// Do we have a repeated start?
			if ( ( channel->sequence < channel->sequence_end ) && ( *channel->sequence == I2C_RESTART ) )
			{

				// Generate a repeated start condition.
				I2C0_C1 |= I2C_C1_RSTA;

				// A restart is processed immediately, so we need to get a new element from our sequence. This is safe, because
				// a sequence cannot end with a RESTART: there has to be something after it. Note that the only thing that can
				// come after a restart is an address write.
				channel->txrx = I2C_WRITING;
				channel->sequence++;
				element = *channel->sequence;
				I2C0_D = element;
			}
			else
			{
				goto i2c_isr_stop;
			}
			break;

		case 1:
			// do not ACK the final read
			I2C0_C1 |= I2C_C1_TXAK;
			*channel->received_data++ = I2C0_D;
			break;

		default:
			*channel->received_data++ = I2C0_D;
			break;
		}

		channel->reads_ahead--;

	}
	// channel->txrx == I2C_WRITING
	else
	{
		// First, check if we are at the end of a sequence.
		if ( channel->sequence == channel->sequence_end )
			goto i2c_isr_stop;

		// We received a NACK. Generate a STOP condition and abort.
		if ( status & I2C_S_RXAK )
		{
			warn_print("NACK Received");
			goto i2c_isr_error;
		}

		// check next thing in our sequence
		element = *channel->sequence;

		// Do we have a restart? If so, generate repeated start and make sure TX is on.
		if ( element == I2C_RESTART )
		{
			I2C0_C1 |= I2C_C1_RSTA | I2C_C1_TX;

			// A restart is processed immediately, so we need to get a new element from our sequence.
			// This is safe, because a sequence cannot end with a RESTART: there has to be something after it.
			channel->sequence++;
			element = *channel->sequence;

			// Note that the only thing that can come after a restart is a write.
			I2C0_D = element;
		}
		else
		{
			if ( element == I2C_READ ) {
				channel->txrx = I2C_READING;
				// How many reads do we have ahead of us ( not including this one )?
				// For reads we need to know the segment length to correctly plan NACK transmissions.
				// We already know about one read
				channel->reads_ahead = 1;
				while (
					(  ( channel->sequence + channel->reads_ahead ) < channel->sequence_end ) &&
					( *( channel->sequence + channel->reads_ahead ) == I2C_READ )
				) {
					channel->reads_ahead++;
				}

				// Switch to RX mode.
				I2C0_C1 &= ~I2C_C1_TX;

				// do not ACK the final read
				if ( channel->reads_ahead == 1 )
				{
					I2C0_C1 |= I2C_C1_TXAK;
				}
				// ACK all but the final read
				else
				{
					I2C0_C1 &= ~( I2C_C1_TXAK );
				}

				// Dummy read comes first, note that this is not valid data!
				// This only triggers a read, actual data will come in the next interrupt call and overwrite this.
				// This is why we do not increment the received_data pointer.
				*channel->received_data = I2C0_D;
				channel->reads_ahead--;
			}
			// Not a restart, not a read, must be a write.
			else
			{
				I2C0_D = element;
			}
		}
	}

	channel->sequence++;
	return;

i2c_isr_stop:
	// Generate STOP ( set MST=0 ), switch to RX mode, and disable further interrupts.
	I2C0_C1 &= ~( I2C_C1_MST | I2C_C1_IICIE | I2C_C1_TXAK );
	channel->status = I2C_AVAILABLE;

	// Call the user-supplied callback function upon successful completion (if it exists).
	if ( channel->callback_fn )
	{
		// Delay 10 microseconds before starting linked function
		delayMicroseconds(10);
		( *channel->callback_fn )( channel->user_data );
	}
	return;

i2c_isr_error:
	// Generate STOP and disable further interrupts.
	I2C0_C1 &= ~( I2C_C1_MST | I2C_C1_IICIE );
	channel->status = I2C_ERROR;
	return;
}