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/*
* PCF-8574 shift register
*
* Copyright (c) 2013 Michael Buesch <m@bues.ch>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "pcf8574.h"
#include "twi_master.h"
#include "util.h"
/* I2C base-address of the PCF-8574 */
#define PCF8574_ADDR_BASE 0x20
/* I2C base-address of the PCF-8574-A */
#define PCF8574A_ADDR_BASE 0x38
/* Wait for the scheduled transfer to finish.
* If there is no scheduled transfer, this function
* returns immediately.
*/
void pcf8574_wait(struct pcf8574_chip *chip)
{
twi_transfer_wait(&chip->xfer, 100);
}
/* Asynchronously write the output states of a PCF-8574 chip.
* The actual write might not have completed after return
* from this function.
* chip: The PCF-8574 chip instance.
* write_value: The 8-bit value to write.
*/
void pcf8574_write(struct pcf8574_chip *chip,
uint8_t write_value)
{
/* Wait for previous transfer to finish, if any. */
pcf8574_wait(chip);
/* Prepare the I2C transfer context. */
chip->xfer.buffer = &write_value;
chip->xfer.write_size = sizeof(write_value);
chip->xfer.read_size = 0;
/* Trigger the I2C transfer. */
twi_transfer(&chip->xfer);
}
/* Synchronously read the input states of a PCF-8574 chip.
* chip: The PCF-8574 chip instance.
* Returns the 8-bit chip-input value.
*/
uint8_t pcf8574_read(struct pcf8574_chip *chip)
{
uint8_t read_value;
/* Wait for previous transfer to finish, if any. */
pcf8574_wait(chip);
/* Prepare the I2C transfer context. */
chip->xfer.buffer = &read_value;
chip->xfer.write_size = 0;
chip->xfer.read_size = sizeof(read_value);
/* Trigger the I2C transfer and wait for it to finish. */
twi_transfer(&chip->xfer);
pcf8574_wait(chip);
return read_value;
}
/* Synchronously write the output states and read the input states
* of a PCF-8574 chip.
* This function first writes and then reads.
* chip: The PCF-8574 chip instance.
* write_value: The 8-bit value to write.
* Returns the 8-bit chip-input value.
*/
uint8_t pcf8574_write_read(struct pcf8574_chip *chip,
uint8_t write_value)
{
uint8_t buffer = write_value;
/* Wait for previous transfer to finish, if any. */
pcf8574_wait(chip);
/* Prepare the I2C transfer context. */
chip->xfer.buffer = &buffer;
chip->xfer.write_size = sizeof(buffer);
chip->xfer.read_size = sizeof(buffer);
/* Trigger the I2C transfer and wait for it to finish. */
twi_transfer(&chip->xfer);
pcf8574_wait(chip);
return buffer;
}
/* Initialize a PCF-8574 context structure.
* address: The I2C sub-address that is physically
* configured on the chip pins (Lower 3 bits).
* chipversion_A: 1: The chip is a PCF-8574-A.
* 0: The chip is a PCF-8574.
* initial_state: 1: All bits are initialized to 1.
* 0: All bits are initialized to 0.
*/
void pcf8574_init(struct pcf8574_chip *chip,
uint8_t address, bool chipversion_A,
bool initial_state)
{
/* Initialize the I2C transfer structure. */
twi_transfer_init(&chip->xfer);
/* Calculate the I2C address, based on the
* Chip version and the sub-address. */
if (chipversion_A)
chip->xfer.address = PCF8574A_ADDR_BASE + (address & 7);
else
chip->xfer.address = PCF8574_ADDR_BASE + (address & 7);
/* Initially write all output states. */
pcf8574_write(chip, initial_state ? 0xFF : 0);
}
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