74 lines
1.3 KiB
C
74 lines
1.3 KiB
C
#include "mystd.h"
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#include <avr/io.h>
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#include <util/twi.h>
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#include "i2c.h"
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void i2c_init(void) {
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// clear the status registers
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TWSR = 0x00;
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// set the i2c clock speed
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TWBR = ((F_CPU / I2C_CLOCK) - 16) / 2;
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}
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void i2c_start(void) {
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// CLR INT | SET MASTER | ENABLE ;
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TWCR = BV(TWINT) | BV(TWSTA) | BV(TWEN);
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// wait until done
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while (!(TWCR & BV(TWINT)))
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;
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}
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void i2c_stop(void) {
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// CLR INT | ENABLE | STOP ;
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TWCR = BV(TWINT) | BV(TWEN) | BV(TWSTO);
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}
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void i2c_write(uint8_t data) {
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// set data to write
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TWDR = data;
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// CLR INT | ENABLE ;
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TWCR = BV(TWINT) | BV(TWEN);
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// wait until done
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while (!(TWCR & BV(TWINT)))
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;
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}
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uint8_t i2c_read_ack(void) {
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TWCR = BV(TWINT) | BV(TWEN) | BV(TWEA);
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while (!(TWCR & BV(TWINT)))
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;
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return TWDR;
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}
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uint8_t i2c_read_nack(void) {
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TWCR = BV(TWINT) | BV(TWEN);
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while (!(TWCR & (1 << TWINT)))
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;
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return TWDR;
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}
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void pca9555_write(uint8_t addr, uint8_t reg, uint8_t value) {
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i2c_start();
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i2c_write((addr << 1) | TW_WRITE); // write mode
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i2c_write(reg);
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i2c_write(value);
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i2c_stop();
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}
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uint8_t pca9555_read(uint8_t addr, uint8_t reg) {
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uint8_t val;
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i2c_start();
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i2c_write((addr << 1) | TW_WRITE);
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i2c_write(reg);
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i2c_start(); // repeated start
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i2c_write((addr << 1) | TW_READ);
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val = i2c_read_nack();
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i2c_stop();
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return val;
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}
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