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Updated Readme with example
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Sovichea Tep
235
twi/twi_master.c
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235
twi/twi_master.c
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/*
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* twi_master.c
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*
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* Created: 09-Jun-19 11:20:17 AM
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* Author: TEP SOVICHEA
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*/
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#include "twi_master.h"
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static ret_code_t tw_start(void)
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{
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/* Send START condition */
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#if DEBUG_LOG
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printf(BG "Send START condition..." RESET);
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#endif
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TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTA);
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/* Wait for TWINT flag to set */
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while (!(TWCR & (1 << TWINT)));
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/* Check error */
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if (TW_STATUS != TW_START && TW_STATUS != TW_REP_START)
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{
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#if DEBUG_LOG
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printf("\n");
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#endif
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return TW_STATUS;
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}
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#if DEBUG_LOG
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printf("SUCCESS\n");
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#endif
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return SUCCESS;
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}
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static void tw_stop(void)
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{
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/* Send STOP condition */
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#if DEBUG_LOG
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puts(BG "Send STOP condition." RESET);
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#endif
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TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
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}
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static ret_code_t tw_write_sla(uint8_t sla)
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{
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/* Transmit slave address with read/write flag */
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#if DEBUG_LOG
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printf(BG "Write SLA + R/W: 0x%02X..." RESET, sla);
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#endif
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TWDR = sla;
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TWCR = (1 << TWINT) | (1 << TWEN);
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/* Wait for TWINT flag to set */
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while (!(TWCR & (1 << TWINT)));
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if (TW_STATUS != TW_MT_SLA_ACK && TW_STATUS != TW_MR_SLA_ACK)
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{
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#if DEBUG_LOG
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printf("\n");
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#endif
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return TW_STATUS;
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}
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#if DEBUG_LOG
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printf("SUCCESS\n");
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#endif
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return SUCCESS;
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}
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static ret_code_t tw_write(uint8_t data)
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{
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/* Transmit 1 byte*/
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#if DEBUG_LOG
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printf(BG "Write data byte: 0x%02X..." RESET, data);
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#endif
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TWDR = data;
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TWCR = (1 << TWINT) | (1 << TWEN);
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/* Wait for TWINT flag to set */
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while (!(TWCR & (1 << TWINT)));
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if (TW_STATUS != TW_MT_DATA_ACK)
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{
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#if DEBUG_LOG
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printf("\n");
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#endif
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return TW_STATUS;
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}
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#if DEBUG_LOG
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printf("SUCCESS\n");
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#endif
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return SUCCESS;
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}
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static uint8_t tw_read(bool read_ack)
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{
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if (read_ack)
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{
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TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWEA);
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while (!(TWCR & (1 << TWINT)));
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if (TW_STATUS != TW_MR_DATA_ACK)
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{
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return TW_STATUS;
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}
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}
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else
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{
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TWCR = (1 << TWINT) | (1 << TWEN);
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while (!(TWCR & (1 << TWINT)));
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if (TW_STATUS != TW_MR_DATA_NACK)
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{
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return TW_STATUS;
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}
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}
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uint8_t data = TWDR;
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#if DEBUG_LOG
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printf(BG "Read data byte: 0x%02X\n" RESET, data);
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#endif
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return data;
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}
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void tw_init(twi_freq_mode_t twi_freq_mode, bool pullup_en)
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{
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DDRC |= (1 << TW_SDA_PIN) | (1 << TW_SCL_PIN);
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if (pullup_en)
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{
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#if DEBUG_LOG
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puts(BG "Enable pull-up resistor." RESET);
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#endif
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PORTC |= (1 << TW_SDA_PIN) | (1 << TW_SCL_PIN);
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}
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else
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{
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PORTC &= ~((1 << TW_SDA_PIN) | (1 << TW_SCL_PIN));
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}
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DDRC &= ~((1 << TW_SDA_PIN) | (1 << TW_SCL_PIN));
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switch (twi_freq_mode)
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{
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case TW_FREQ_100K:
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/* Set bit rate register 72 and prescaler to 1 resulting in
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SCL_freq = 16MHz/(16 + 2*72*1) = 100KHz */
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TWBR = 72;
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break;
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case TW_FREQ_250K:
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/* Set bit rate register 24 and prescaler to 1 resulting in
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SCL_freq = 16MHz/(16 + 2*24*1) = 250KHz */
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TWBR = 24;
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break;
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case TW_FREQ_400K:
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/* Set bit rate register 12 and prescaler to 1 resulting in
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SCL_freq = 16MHz/(16 + 2*12*1) = 400KHz */
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TWBR = 12;
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break;
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default: break;
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}
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}
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ret_code_t tw_master_transmit(uint8_t slave_addr, uint8_t* p_data, uint8_t len, bool repeat_start)
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{
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ret_code_t error_code;
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/* Send START condition */
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error_code = tw_start();
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if (error_code != SUCCESS)
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{
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return error_code;
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}
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/* Send slave address with WRITE flag */
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error_code = tw_write_sla(TW_SLA_W(slave_addr));
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if (error_code != SUCCESS)
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{
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return error_code;
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}
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/* Send data byte in single or burst mode */
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for (int i = 0; i < len; ++i)
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{
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error_code = tw_write(p_data[i]);
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if (error_code != SUCCESS)
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{
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return error_code;
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}
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}
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if (!repeat_start)
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{
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/* Send STOP condition */
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tw_stop();
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}
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return SUCCESS;
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}
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ret_code_t tw_master_receive(uint8_t slave_addr, uint8_t* p_data, uint8_t len)
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{
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ret_code_t error_code;
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/* Send START condition */
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error_code = tw_start();
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if (error_code != SUCCESS)
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{
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return error_code;
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}
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/* Write slave address with READ flag */
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error_code = tw_write_sla(TW_SLA_R(slave_addr));
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if (error_code != SUCCESS)
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{
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return error_code;
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}
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/* Read single or multiple data byte and send ack */
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for (int i = 0; i < len-1; ++i)
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{
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p_data[i] = tw_read(TW_READ_ACK);
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}
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p_data[len-1] = tw_read(TW_READ_NACK);
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/* Send STOP condition */
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tw_stop();
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return SUCCESS;
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}
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39
twi/twi_master.h
Normal file
39
twi/twi_master.h
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@@ -0,0 +1,39 @@
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/*
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* twi_master.h
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*
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* Created: 09-Jun-19 11:20:04 AM
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* Author: TEP SOVICHEA
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*/
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#ifndef TWI_MASTER_H_
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#define TWI_MASTER_H_
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#include <avr/io.h>
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#include <util/twi.h>
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#include <stdbool.h>
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#define DEBUG_LOG 0
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#define SUCCESS 0
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#define TW_SCL_PIN PORTC5
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#define TW_SDA_PIN PORTC4
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#define TW_SLA_W(ADDR) ((ADDR << 1) | TW_WRITE)
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#define TW_SLA_R(ADDR) ((ADDR << 1) | TW_READ)
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#define TW_READ_ACK 1
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#define TW_READ_NACK 0
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typedef uint16_t ret_code_t;
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typedef enum {
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TW_FREQ_100K,
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TW_FREQ_250K,
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TW_FREQ_400K
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} twi_freq_mode_t;
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void tw_init(twi_freq_mode_t twi_freq, bool pullup_en);
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ret_code_t tw_master_transmit(uint8_t slave_addr, uint8_t* p_data, uint8_t len, bool repeat_start);
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ret_code_t tw_master_receive(uint8_t slave_addr, uint8_t* p_data, uint8_t len);
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#endif /* TWI_MASTER_H_ */
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