Hi Team Toradex,
I hope you are doing well.
Setup 1)
Below are our hardware and firmware specifications.
Operating System : Android 10
Kernel Version : 5.4
SOM : IMX8QM
Carrier Board : IXORA Carrier board v1.1.
SPI Slave : MAX7219 SPI dot matrix display
We are trying to up the MAX7219 LED Dot Matrix display from the user space (We don’t have any linux kernel driver). This is the link of the display.
We are facing the communication problem of SPI bus in our setup. The chip select pin is not getting low, and the clock is not being generated. Below are the device tree nodes of the SPI bus that we have tried. The use space code for the display is zipped and attached.
trpmk.tar.gz (3.1 KB)
.
1)
/* Apalis SPI1 */
&lpspi0 {
#address-cells = <1>;
#size-cells = <0>;
fsl,spi-num-chipselects = <1>;
pinctrl-names = “default”;
pinctrl-0 = <&pinctrl_lpspi0 &pinctrl_lpspi0_cs>;
cs-gpios = <&lsio_gpio3 5 GPIO_ACTIVE_LOW> ;
status = “okay”;
spidev0: spi@0 {
compatible = "toradex,evalspi";
reg = <0>;
spi-max-frequency = <12000000>;
};
};
/* Apalis SPI1 */
pinctrl_lpspi0: lpspi0grp {
fsl,pins = <
IMX8QM_SPI0_SCK_DMA_SPI0_SCK 0x0600004c
IMX8QM_SPI0_SDO_DMA_SPI0_SDO 0x0600004c
IMX8QM_SPI0_SDI_DMA_SPI0_SDI 0x0600004c
IMX8QM_SPI0_CS0_DMA_SPI0_CS0 0x0600004c
>;
};
pinctrl_lpspi0_cs: lpspi0cs {
fsl,pins = <
IMX8QM_SPI0_CS0_LSIO_GPIO3_IO05 0x21
>;
};
2)
/* Apalis SPI1 */
&lpspi0 {
#address-cells = <1>;
#size-cells = <0>;
fsl,spi-num-chipselects = <1>;
pinctrl-names = “default”;
pinctrl-0 = <&pinctrl_lpspi0>;
cs-gpios = <&lsio_gpio3 5 GPIO_ACTIVE_LOW> ;
status = “okay”;
spidev0: spi@0 {
compatible = "toradex,evalspi";
reg = <0>;
spi-max-frequency = <12000000>;
};
};
/* Apalis SPI1 */
pinctrl_lpspi0: lpspi0grp {
fsl,pins = <
IMX8QM_SPI0_SCK_DMA_SPI0_SCK 0x0600004c
IMX8QM_SPI0_SDO_DMA_SPI0_SDO 0x0600004c
IMX8QM_SPI0_SDI_DMA_SPI0_SDI 0x0600004c
IMX8QM_SPI0_CS0_LSIO_GPIO3_IO05 0x0600004c
>;
};
The same code we have compiled (Compiled inside Raspberry Pi) in Raspberry Pi and run from the user space, and it is working. We have also tried (only for testing, not part of the project) to communicate with the SPI sensors : accelerometer, pressure sensor from the user space, but we are not able to bring up any of the SPI sensor. The same sensor were working fine with the Raspberry Pi from the user space.
Kindly help us to solve this issue.
Setup 2)
Below are our hardware and firmware specifications.
Operating System : Android 10
Kernel Version : 5.4
SOM : IMX8QM
Carrier Board : Our in-house board
-
We have also tried to communicate to the dot matrix display by connecting it to our carrier board and facing the same issue, we are not able to communicate with the display, the chip select pin is not getting low and clock is not being generated. The schematic and pin layout of the hardware are attached for your reference.
-
we have a question regarding the design (Our end goal is to connect the dot matrix display to our in house board on SPI): Below is the schematic image of SPI lined of the Ixora board. There are 22 ohms resistors are connected on the output of the SPI bus and connector X27, That’s makes the 22R resistor in series between the SPI lines of the SOM module and the Display module.
What is the use case of the 22R resistor on SPI lines? Can we connect the 0hms instead of the 22 ohms? How to decide the resistor values if it is matters in solid communication between the SOM and slave device ? Kindly share your views and answer on this.
- Ixora carrier board design
Our inhouse design
