Revision 276
cleaned up library - dos2unix and delete-trailing-whitespace
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/** |
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* Copyright (c) 2007 Colony Project |
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*
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* |
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* Permission is hereby granted, free of charge, to any person |
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* obtaining a copy of this software and associated documentation |
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* files (the "Software"), to deal in the Software without |
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* copies of the Software, and to permit persons to whom the |
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* Software is furnished to do so, subject to the following |
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* conditions: |
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*
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* |
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* The above copyright notice and this permission notice shall be |
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* included in all copies or substantial portions of the Software. |
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*
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* |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES |
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
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/** |
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* @file i2c.c |
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* @brief Implemenation of I2C communications protocol |
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*
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* |
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* In the case where you have master sends and then a master request to the same |
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* address, you will not give up control of the line because the send and |
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* request addresses are seen as different addresses. In between it will send a |
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#include "ring_buffer.h" |
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/** |
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* @defgroup i2c I2C
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* @defgroup i2c I2C |
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* |
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* @brief Provides Inter-Interconnected-Communications (I2C) |
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*
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* Initiates I2C functions on an ATMega128 which has a fully hardware Two Wire
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* |
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* Initiates I2C functions on an ATMega128 which has a fully hardware Two Wire |
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* Interface (TWI) module. Any Atmel chip with this hardware should be able to |
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* use the software. |
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* |
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* This code will operate in a multi-master enviornment and can be either a |
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* slave or a master at any time (as long as they are not one or the other at |
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* the moment. You can queue up multiple transmission modes in the buffer up to
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* the moment. You can queue up multiple transmission modes in the buffer up to |
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* the buffer size. The buffer is implemented as a ring buffer. |
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* |
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* It is implemented using callback functions. Whenever you want to send a packet |
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* so you must either buffer the inputs or handle each one separately. |
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* |
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* On errors we will simply flush the entire buffer. |
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*
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* |
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* For information on how I2C operates, read the wikipedia article |
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* http://en.wikipedia.org/wiki/I2c |
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* for a good explanation of how it works. |
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* @{ |
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*/ |
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/**
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/** |
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* @brief Set bit rate 12 = 100kbit/s (max speed setting is 10 for an |
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* 8 MHz clock). It is a divider, so the lower the number the faster the speed. |
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*/ |
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RING_BUFFER_CLEAR(i2c_write_buff); |
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RING_BUFFER_CLEAR(i2c_addr_buff); |
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/* enables twi interrupt, automatic ack sending, and all twi hardware */ |
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TWCR = (_BV(TWEA) | _BV(TWEN) | _BV(TWIE)); |
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/* sets the address (it is stored in the 7 most significant bits) and allows |
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* global messages to be accepted */ |
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TWAR = (addr << 1) | 1; |
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return 0; |
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} |
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RING_BUFFER_ADD(i2c_write_buff, data[i]); |
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RING_BUFFER_ADD(i2c_addr_buff, dest << 1); |
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} |
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/* re-enable the interrupts */ |
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sei(); |
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/* send the start bit, only if this device is not currently master */ |
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if(!start_flag) { |
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start_flag = 1; |
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TWCR |= _BV(TWSTA); |
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TWCR |= _BV(TWINT); |
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} |
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return 0; |
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} |
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/** |
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* @brief Send a master request to the destination |
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* |
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* @param dest The destination that we want to receive information from. |
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* |
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* @return 0 for success, nonzero for failure |
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**/
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**/ |
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int i2c_request(char dest) { |
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if(RING_BUFFER_FULL(i2c_write_buff)) |
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return -1; |
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RING_BUFFER_ADD(i2c_write_buff, 0); |
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RING_BUFFER_ADD(i2c_addr_buff, (dest << 1) | 1); |
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if(!start_flag) { |
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start_flag = 1; |
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TWCR |= _BV(TWSTA); |
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TWCR |= _BV(TWINT); |
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} |
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return 0; |
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} |
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/** @} **/ |
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/** |
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* @brief Interrupt to handle I2C interrupts from the I2C hardware. |
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*
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* |
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* Uses the status codes from the I2C register to handle the events |
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* needed to advance in I2C stages. For instance, you will get a bit for |
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* receiving a start ack, then a address ack, then a data ack, etc. |
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* of what modes the send is in. |
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* |
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* Errors are handled here as well. |
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**/
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**/ |
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ISR(TWI_vect) { |
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static char data_to_send; |
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static char addr_to_send = -1; |
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char addr, statusCode; |
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//Get status code (only upper 5 bits) |
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statusCode = (TWSR & 0xF8); |
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* ring_buffer will not be empty */ |
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RING_BUFFER_REMOVE(i2c_addr_buff, addr_to_send); |
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RING_BUFFER_REMOVE(i2c_write_buff, data_to_send); |
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/* first send the address */ |
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TWDR = addr_to_send;
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TWDR = addr_to_send; |
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//Turn off start bits |
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TWCR &= ~_BV(TWSTA); |
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break; |
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TWDR = data_to_send; |
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PORTG &= ~_BV(PG2); |
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break; |
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//Master Transmit - Data sent succesfully |
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case TW_MT_DATA_ACK:
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case TW_MT_DATA_ACK: |
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//If there is still data to send |
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if(!RING_BUFFER_EMPTY(i2c_write_buff)) { |
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RING_BUFFER_PEEK(i2c_addr_buff, addr); |
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//Still data for this address |
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if (addr == addr_to_send) { |
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RING_BUFFER_REMOVE(i2c_addr_buff, addr); |
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/* there are no bytes to send */ |
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TWCR |= _BV(TWSTO); |
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start_flag = 0; |
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break;
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break; |
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//Master Transmit - Slave sends a nack, transmit is done |
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case TW_MT_DATA_NACK: |
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PORTG |= _BV(PG2); |
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TWCR |= _BV(TWSTO); |
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start_flag = 0; |
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break; |
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//Master Receive - Address sent succesfully |
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case TW_MR_SLA_ACK: |
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PORTG |= _BV(PG2); |
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break; |
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//Master Receive - Data received succesfully |
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case TW_MR_DATA_ACK: |
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if(master_recv_function) { |
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} |
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} |
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break; |
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//Master Receive - Slave sends a nack, transmission is done
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//Master Receive - Slave sends a nack, transmission is done |
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case TW_MR_DATA_NACK: |
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TWCR |= _BV(TWEA); |
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//If there is still data to send |
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if(!RING_BUFFER_EMPTY(i2c_write_buff)) { |
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TWCR |= _BV(TWSTA); |
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break; |
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} |
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/* there are no bytes to send */ |
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TWCR |= _BV(TWSTO); |
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start_flag = 0;
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start_flag = 0; |
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break; |
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//Slave Transmit - Address received |
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case TW_ST_SLA_ACK: |
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break; |
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//Slave Transmit - Nack received, no data requsted |
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case TW_ST_DATA_NACK: |
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break; |
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//Slave Transmit - Data requested, ack received |
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case TW_ST_DATA_ACK: |
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if (slave_send_function) { |
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TWDR = slave_send_function(); |
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} |
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break; |
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//Slave Receive - Address received
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//Slave Receive - Address received |
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case TW_SR_SLA_ACK: |
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break; |
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//Slave Receive - Data received, ack returned |
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case TW_SR_DATA_ACK: |
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if(slave_recv_function) { |
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slave_recv_function(TWDR); |
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} |
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break; |
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//Stop sent
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//Stop sent |
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case TW_SR_STOP: |
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break; |
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//Problem on the bus, reset everything |
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default: |
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TWCR |= _BV(TWSTO); |
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start_flag = 0; |
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RING_BUFFER_CLEAR(i2c_write_buff); |
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RING_BUFFER_CLEAR(i2c_addr_buff);
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RING_BUFFER_CLEAR(i2c_addr_buff); |
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} |
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/* Toggle TWINT so that it resets and executes the commands */ |
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TWCR |= _BV(TWINT); |
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} |
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