Hi,
- On jetson Nano I’ve ena ble the SPI0 (pins 19, 21, 23, 24, 26 on J41) with jeston-io utility. I’ts OK and I can see /dev/spidev0.0
- I use spidev (in CC+) to manage the SPI data bus : See https://01.org/linuxgraphics/gfx-docs/drm/spi/spidev.html
- SPI bus speed is set to 1MHz
- The transmit (from Nano to device) is working well and I can see (on a logic analyzer) that the device replies correctly: see attached
- The pb is that the byte read in the SPI rx_buffer are always 0…like if only the SPI MOSI was enable but not MISO …!
I’ve tried also several things to fix that (changing the SPI_MODE, a jumper between pins 19/21 of J41 to get same data received than emitted, …)
here is the short C code I use:
To init the SPI bus /dev/spidev0.0
int SPI::initSPI(char *device, unsigned int speed, unsigned int delay_usecs, unsigned char bits_per_word, unsigned char cs_change)
{
memset(&config, 0, sizeof config);
memset(spi_rxBuf, 0, sizeof spi_rxBuf);
memset(spi_txBuf, 0, sizeof spi_txBuf);
config.rx_buf = (unsigned long) &spi_rxBuf;
config.tx_buf = (unsigned long) &spi_txBuf;
config.delay_usecs = delay_usecs; // delay after the last bit transfer before optionally deselecting the device before the next transfer
config.speed_hz = speed; // Bus speed in Hz
config.bits_per_word = bits_per_word;
config.cs_change = cs_change; // True to deselect device before starting the next transfer
fd = open(device, O_RDWR); // fd is a private file descriptor
usleep(1000); // Wait a bit after the opening
if (fd < 0)
return -1;
return 0; // return OK
}
To perform a synchronous transfer to/from device on /dev/spidev0.0
spi_dsPIC.spi_txBuf[0] = 0x55; // Fill buffer to be sent
spi_dsPIC.spi_txBuf[1] = 0xC0;
spi_dsPIC.spi_txBuf[2] = 4;
spi_dsPIC.spi_txBuf[3] = 0;
spi_dsPIC.spi_txBuf[4] = 0;
spi_dsPIC.spi_txBuf[5] = 0;
spi_dsPIC.spi_txBuf[6] = 0;
spi_dsPIC.spi_txBuf[7] = 0;
config.len = 8; // complete the len in the structure
ioctl(fd, SPI_IOC_MESSAGE(1), &config); // normally spi_rxBuf contains reply
We are stuck on this pb since 2 days.
Thanks for help.