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Actually implement Linux SPI access

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This commit is contained in:
Adam Novak 2022-02-13 18:40:30 -05:00
parent 271ee75584
commit c46ec5778d
3 changed files with 59 additions and 7 deletions
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47
LoRa.cpp
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@ -11,6 +11,10 @@
#include <unistd.h>
// And we need to use the filesystem and IOCTLs instead of an SPI global
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>
// And to have memset
#include <cstring>
// And we need to be able to report errors
#include <stdio.h>
#include <errno.h>
@ -683,6 +687,7 @@ uint8_t ISR_VECT LoRaClass::singleTransfer(uint8_t address, uint8_t value)
uint8_t response;
#if LIBRARY_TYPE == LIBRARY_ARDUINO
// Select chip, send address, and send/read data, the Arduino way
digitalWrite(_ss, LOW);
SPI.beginTransaction(_spiSettings);
@ -692,7 +697,47 @@ uint8_t ISR_VECT LoRaClass::singleTransfer(uint8_t address, uint8_t value)
digitalWrite(_ss, HIGH);
#elif LIBRARY_TYPE == LIBRARY_C
// Select chip, send address, and send/read data, the Linux way
// In Linux, chip select is automatically turned off outside of transactions.
int status;
// Configure SPI speed and mode to match settings
status = ioctl(_fd, SPI_IOC_WR_MODE, &_spiSettings.mode);
if (status < 0) {
perror("ioctl SPI_IOC_WR_MODE failed");
exit(1);
}
status = ioctl(_fd, SPI_IOC_WR_LSB_FIRST, &_spiSettings.bitness);
if (status < 0) {
perror("ioctl SPI_IOC_WR_LSB_FIRST failed");
exit(1);
}
status = ioctl(_fd, SPI_IOC_WR_MAX_SPEED_HZ, &_spiSettings.frequency);
if (status < 0) {
perror("ioctl SPI_IOC_WR_MAX_SPEED_HZ failed");
exit(1);
}
// We have two transfers: one send-only to send the address, and one
// send/receive, to send the value and get the response.
struct spi_ioc_transfer xfer[2];
memset(xfer, 0, sizeof xfer);
xfer[0].tx_buf = (unsigned long) &address;
xfer[0].len = 1;
xfer[1].tx_buf = (unsigned long) &value;
xfer[1].rx_buf = (unsigned long) &response;
xfer[1].len = 1;
// Do the transaction
status = ioctl(_fd, SPI_IOC_MESSAGE(2), xfer);
if (status < 0) {
perror("ioctl SPI_IOC_MESSAGE failed");
exit(1);
}
#else
#error "SPI transfer not implemented for library type"
#endif