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linux: Add support for bi-directional SPI communication 

Signed-off-by: Ricardo Amézquita <ramezquitao@cihologramas.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Ricardo Amezquita 2018-06-17 19:57:58 -05:00 committed by Kevin O'Connor
parent 6a60fe998d
commit 940db6bd70
2 changed files with 33 additions and 5 deletions
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1
src/linux/gpio.h
View File

@ -21,6 +21,7 @@ void gpio_adc_cancel_sample(struct gpio_adc g);
struct spi_config {
int fd;
int rate;
};
struct spi_config spi_setup(uint32_t bus, uint8_t mode, uint32_t rate);
void spi_prepare(struct spi_config config);

37
src/linux/spidev.c
View File

@ -5,7 +5,10 @@
// This file may be distributed under the terms of the GNU GPLv3 license.
#include <fcntl.h> // open
#include <linux/spi/spidev.h> // SPI_IOC_MESSAGE
#include <stdio.h> // snprintf
#include <string.h> // memset
#include <sys/ioctl.h> // ioctl
#include <unistd.h> // write
#include "command.h" // DECL_COMMAND
#include "gpio.h" // spi_setup
@ -53,7 +56,12 @@ spi_setup(uint32_t bus, uint8_t mode, uint32_t rate)
{
int bus_id = (bus >> 8) & 0xff, dev_id = bus & 0xff;
int fd = spi_open(bus_id, dev_id);
return (struct spi_config) { fd };
int ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &rate);
if (ret < 0) {
report_errno("ioctl set max spi speed", ret);
shutdown("Unable to set SPI speed");
}
return (struct spi_config) { fd , rate};
}
void
@ -65,10 +73,29 @@ void
spi_transfer(struct spi_config config, uint8_t receive_data
, uint8_t len, uint8_t *data)
{
int ret = write(config.fd, data, len);
if (ret < 0) {
report_errno("write spi", ret);
shutdown("Unable to write to spi");
if (!len)
return;
if (receive_data) {
struct spi_ioc_transfer transfer;
memset(&transfer, 0, sizeof(transfer));
transfer.tx_buf = (uintptr_t)data;
transfer.rx_buf = (uintptr_t)data;
transfer.len = len;
transfer.speed_hz = config.rate;
transfer.bits_per_word = 8;
transfer.cs_change = 0;
int ret = ioctl(config.fd, SPI_IOC_MESSAGE(1), &transfer);
if (ret < 0) {
report_errno("spi ioctl", ret);
shutdown("Unable to issue spi ioctl");
}
} else {
int ret = write(config.fd, data, len);
if (ret < 0) {
report_errno("write spi", ret);
shutdown("Unable to write to spi");
}
}
}