FelipeMdeO commented on issue #13855:
URL: https://github.com/apache/nuttx/issues/13855#issuecomment-2411572560
Hello @eren-terzioglu
below you can see an example:
```
#include <nuttx/config.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
/****************************************************************************
* Public Functions
****************************************************************************/
#define MASTER 0
#ifdef MASTER
#define SOURCE_FILE "/dev/spi2"
#else
#define SOURCE_FILE "/dev/spislv2"
#endif
#define BUFFER_SIZE 256
/****************************************************************************
* hello_slave_main
****************************************************************************/
int main(int argc, FAR char *argv[])
{
int fd;
char buffer[BUFFER_SIZE];
ssize_t bytes_read;
printf("Slave started!!\n");
fd = open(SOURCE_FILE, O_RDWR);
if (fd < 0)
{
printf("Failed to open %s: %s\n", SOURCE_FILE, strerror(errno));
return 0;
}
while(1)
{
// Read the number from the source file
printf("Slave: Reading from %s\n", SOURCE_FILE);
bytes_read = read(fd, buffer, BUFFER_SIZE - 1);
if (bytes_read < 0)
{
printf("Failed to read from %s: %s\n", SOURCE_FILE,
strerror(errno));
close(fd);
return 0;
}
else if (bytes_read > 0)
{
buffer[bytes_read] = '\0';
printf("Slave: Read value '%s' from %s\n", buffer, SOURCE_FILE);
// Write the same value back
printf("Slave: Writing value '%s' back to %s\n", buffer,
SOURCE_FILE);
if (write(fd, buffer, strlen(buffer)) < 0)
{
printf("Failed to write to %s: %s\n", SOURCE_FILE,
strerror(errno));
close(fd);
return 0;
}
}
sleep(1);
}
close(fd);
return 0;
}
```
In this example I am always answer empty buffer to master, but you will see
that the master will print data.
If you have one available, please use a logic analyzer.
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