SPI Code Instability - Raspbian (Debian) Linux on RPi - c++

Question

I am trying to get my software to read and write writing a CAT25512 EEPROM from a Raspberry Pi 3 with Raspbian (Debian) Linux. Before writing to the memory a Write Enable Latch (WEL) has to be set with command 0x06. This write is successful. It is then checked with the read status register command 0x05, which also succeeds. Then the write, read, and successive status read commands get no response and/or fail.
I have tried adding some delays to wait for the HW. I have also restructured the code many times.
I apologize in advance for the complete file, but I'm not sure where the problem lies.
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>
#include <string>
#include <cstring>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
#define WAIT_FOR_EEPROM(a) do { for (int z=0; z<0x3FFF; z++); } while (eepromBusy((a) != 0x02));
const char *device = "/dev/spidev0.0";
uint8_t mode=SPI_MODE_0;
uint8_t bits=8;
uint32_t baud=500000;
uint8_t buffer[4] = {0};
int transfer(int spi_file, uint8_t* buffer, int length); // Prototype
int eepromBusy(int spi_file) {
buffer[0] = 0x05;
buffer[1] = 0x00;
transfer(spi_file, buffer, 2);
return (buffer[1]);
}
int main() {
int fd = open(device,O_RDWR);
if (fd < 0) printf("can't open device");
int ret;
ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
if (ret == -1) printf("can't set spi mode");
ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
if (ret == -1) printf("can't set bits!");
ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &baud);
if (ret == -1) printf("can't set speed!");
ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
if (ret == -1) printf("can't set spi mode");
ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
if (ret == -1) printf("can't set bits!");
ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &baud);
if (ret == -1) printf("can't set speed!");
printf("spi mode set as %u\n", mode);
printf("bits per byte set as %u\n", bits);
printf("max speed set at %u\n", baud);
do {
// Write Enable
buffer[0] = 0x06;
transfer(fd, buffer, 1);
// Read Status
buffer[0] = 0x05;
buffer[1] = 0x00;
transfer(fd, buffer, 2);
} while (!(buffer[1] & 0x02));
printf("Status Reg: %x\n", buffer[1]);
WAIT_FOR_EEPROM(fd)
// usleep(100);
// Write Byte
buffer[0] = 0x02;
buffer[1] = 0x00;
buffer[2] = 0x10;
buffer[3] = 0xAA;
transfer(fd, buffer, 4);
/* uint8_t busy = -1;
do {
usleep(50);
buffer[0] = 0x05;
buffer[1] = 0x00;
transfer(fd, buffer, 2);
busy = buffer[1] & 0x01;
} while (busy);
*/
WAIT_FOR_EEPROM(fd)
// Read Byte
buffer[0] = 0x03;
buffer[1] = 0x00;
buffer[2] = 0x10;
buffer[3] = 0x00;
transfer(fd, buffer, 4);
printf("Received byte: %i\n", buffer[3]);
if (close(fd) > 0) printf("can't close device");
return 0;
}
int transfer(int spi_file, uint8_t *buffer, int length) {
//struct spi_ioc_transfer spi[length] = {0};
int ret = -1;
struct spi_ioc_transfer tr[length] = {0};
for (int x=0; x<length; ++x) {
tr[x].tx_buf = (unsigned long)(buffer+x);
tr[x].rx_buf = (unsigned long)(buffer+x);
tr[x].len = sizeof(*(buffer+x));
tr[x].delay_usecs = 0;
tr[x].speed_hz = baud;
tr[x].bits_per_word = bits;
tr[x].cs_change = 0;
};
ret = ioctl(spi_file, SPI_IOC_MESSAGE(length), &tr);
if (ret < 1) printf("Transfer Error!!! First Byte Was: 0x%x\n", buffer[0]);
return ret;
}
I am currently getting the Transfer Error!!! First Byte Was: 0x5 error twice, indicating that the WAIT_FOR_EEPROM(fd) commands are not properly being executed.
In the beginning, the WEL bit is set with command 0x06 and the status is correctly reported as 2. The data read from EEPROM has read out as 0 or 211 depending on how I've tweaked the code. It should be 0xAA (170).
I would appreciate any suggestions.

Answer 1

I guess the transfer() function is responsible to setup and execute one SPI command per call.
Why you are using an array of 'struct spi_ioc_transfer' ?
Why are you loop over the number of bytes in buffer and setup a 'spi_ioc_transfer' structure for each ?
Take a look at https://raw.githubusercontent.com/raspberrypi/linux/rpi-3.10.y/Documentation/spi/spidev_test.c