SPI Communication Issue with MISO/MOSI on i.MX8MP for LED Board

MJD — Wed, 01 Jan 2025 14:12:08 GMT

Hi NXP Team,

We are working on a custom board with the i.MX8MP processor and are trying to establish SPI communication with an LED board connected via the following pins:

UART3_CTS_3V3 = ECSPI1_MISO = LED_DOUT_3V3
UART3_RXD_3V3 = ECSPI1_MOSI = LED_DIN_3V3

We have the following device tree configuration:

269 &ecspi1 {

270 pinctrl-names = "default";

271 pinctrl-0 = <&pinctrl_ecspi1>;

272 status = "okay";

273

274 leds-gpio@1 {

275 compatible = "custom,leds-gpio"; /* Update to your specific LED driver */

276 reg = <1>; /* SPI chip select 0 */

278 spi-max-frequency = <1200000>; /* 1 MHz */

279 status = "okay";

282 leds {

283 compatible = "spi,rgb-leds";

284 led-names = "red", "green", "blue";

285 led-count = <8>; /* Adjust based on the number of LEDs */

286 };

287 };

288 };

1154 pinctrl_ecspi1: ecspi1grp {

1155 fsl,pins = <

1157 MX8MP_IOMUXC_ECSPI1_MOSI__ECSPI1_MOSI 0x00

1158 MX8MP_IOMUXC_ECSPI1_MISO__ECSPI1_MISO 0x00

1159 >;

1160 };

Current Issues:

No Chip Select (CS) or SCLK Connection
The LED board is only connected to the MISO and MOSI pins, without a CS pin or SCLK connection. Can SPI communication be achieved with only these two pins?
Driver Initialization
The SPI driver initializes without errors, as seen in the logs:
[ 142.944595] LED count not specified in DT, defaulting to 8 [ 142.950130] Sending data to RGB LEDs... [ 142.950655] SPI data sent successfully [ 142.950669] leds-gpio spi1.1: RGB LED SPI driver initialized [ 142.956376] RGB LED SPI driver initialized
Device Testing Fails
The device appears under /sys/bus/spi/devices/spi1.0:
root@imx8mp-lpddr4-evk:~# cat /sys/bus/spi/devices/spi1.0/modalias spi:leds-gpio
However, when attempting to test the device using spidev_test, it fails:
root@imx8mp-lpddr4-evk:~# spidev_test -D /dev/spidev1.0 -v
can't open device: No such file Aborted
No LEDs in /sys/class/leds
The LEDs are not exposed under /sys/class/leds, and I cannot control them directly:
root@imx8mp-lpddr4-evk:~# ls /sys/class/leds/
mmc1:: mmc2::

Questions:

Is the above DTS configuration correct for SPI communication over MISO and MOSI without CS or SCLK?
Can SPI communication with the LED board be established using only MISO and MOSI?
How can I resolve the issue with the device node /dev/spidev1.0 not being accessible?
What changes are required to expose the LEDs in /sys/class/leds for direct control?

Any guidance or suggestions would be greatly appreciated.

Thank you,

Re: SPI Communication Issue with MISO/MOSI on i.MX8MP for LED Board

Zhiming_Liu — Mon, 06 Jan 2025 01:03:06 GMT

Hello,

Both CS and SCLK are typically essential, along with MOSI and MISO. Without these, the communication protocol would not function correctly.

Best Regards,
Zhiming

i.MX ProcessorsのトピックRe: SPI Communication Issue with MISO/MOSI on i.MX8MP for LED Board

SPI Communication Issue with MISO/MOSI on i.MX8MP for LED Board

Current Issues:

Questions:

Re: SPI Communication Issue with MISO/MOSI on i.MX8MP for LED Board