DART-6UL SPI

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DART-6UL/VAR-SOM-MX7 - SPI

In this example we will show how to configure SPI 1 and SPI 2 to work on SOM

1 Kernel configuration

Verify that the User mode SPI driver (CONFIG_SPI_SPIDEV) is enabled in your kernel configuration:

  • In menuconfig: Device Drivers -> SPI support -> <*> User mode SPI device driver support

2 SPI 1 on 6UL Custom Board and Condcerto Board

2.1 Add spidev to your device tree

&ecspi1 {
	fsl,spi-num-chipselects = <1>;
	cs-gpios = <&gpio4 26 0>;
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_ecspi1_1>;
	status = "okay";

        chip1: spidev@0 {
               compatible = "var,spidev";
               spi-max-frequency = <12000000>;
               reg = <0>;
        };
};

2.2 Add pin control to your device tree

&iomuxc {
	pinctrl_ecspi1_1: ecspi1grp {
		fsl,pins = <
			MX6UL_PAD_CSI_DATA07__ECSPI1_MISO       0x100b1
			MX6UL_PAD_CSI_DATA06__ECSPI1_MOSI       0x100b1
			MX6UL_PAD_CSI_DATA04__ECSPI1_SCLK       0x100b1
			MX6UL_PAD_CSI_DATA05__GPIO4_IO26        0x100b1
		>;
	};

};

2.3 Pins on the boards

pins 6UL Custom Board Concerto Board
MISO J11.8 J14.1
MOSI J11.6 J14.2
SCLK J11.2 J14.4
chipselect J11.4 J14.6

Note: The pins here were set arbitrarily. You should set them based on your hardware design, and make sure they are not conflicting with other devices in the device tree.
you can also have multiple chip selects.

3 SPI 2 on 6UL Custom Board

3.1 Add spidev to your device tree

&ecspi2 {
	fsl,spi-num-chipselects = <1>;
	cs-gpios = <&gpio4 22 0>;
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_ecspi2_1>;
	status = "okay";

	spidev@0 {
               compatible = "var,spidev";
               spi-max-frequency = <12000000>;
               reg = <0>;
        };
};

3.2 Add pin control to your device tree

&iomuxc {
	pinctrl_ecspi2_1: ecspi2grp {
		fsl,pins = <
			MX6UL_PAD_CSI_DATA03__ECSPI2_MISO	0x100b1 /* from J6.7 */
			MX6UL_PAD_CSI_DATA02__ECSPI2_MOSI	0x100b1 /* from J13.2 */
			MX6UL_PAD_CSI_DATA00__ECSPI2_SCLK	0x100b1 /* from J11.9 */
			MX6UL_PAD_CSI_DATA01__GPIO4_IO22	0x100b1 /* from J6.5 */
		>;
	};
};

Note: The pins here were set arbitrarily. You should set them based on your hardware design, and make sure they are not conflicting with other devices in the device tree.
you can also have multiple chip selects.

4 SPI 2 on Concerto Board

4.1 Add spidev to your device tree

&ecspi2 {
	fsl,spi-num-chipselects = <1>;
	cs-gpios = <&gpio1 29 0>;
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_ecspi2_1>;
	status = "okay";

	spidev@0 {
               compatible = "var,spidev";
               spi-max-frequency = <12000000>;
               reg = <0>;
        };
};

4.2 Add pin control to your device tree

&iomuxc {
	pinctrl_ecspi2_1: ecspi2grp {
		fsl,pins = <
			MX6UL_PAD_UART5_TX_DATA__ECSPI2_MOSI	0x100b1 /* from J18.12 */
			MX6UL_PAD_UART5_RX_DATA__ECSPI2_MISO	0x100b1 /* from J18.17 */
			MX6UL_PAD_UART4_TX_DATA__ECSPI2_SCLK	0x100b1 /* from J18.18 */
			MX6UL_PAD_UART4_RX_DATA__GPIO1_IO29	0x100b1 /* from J18.11 */
		>;
	};
};

Note: The pins here were set arbitrarily. You should set them based on your hardware design, and make sure they are not conflicting with other devices in the device tree.
you can also have multiple chip selects.

5 SPI 4 on Symphony Board (ENET2 not enabled)

5.1 Add spidev to your device tree

&ecspi4 {
	fsl,spi-num-chipselects = <1>;
	cs-gpios = <&gpio2 15 0>;
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_ecspi4>;
	status = "okay";

	spidev@0 {
               compatible = "var,spidev";
               spi-max-frequency = <12000000>;
               reg = <0>;
        };
};

5.2 Add pin control to your device tree

&iomuxc {
	pinctrl_ecspi4: ecspi4grp {
		fsl,pins = <
			MX6UL_PAD_ENET2_TX_EN__ECSPI4_MOSI	0x100b1 /* from J16.8 */
			MX6UL_PAD_ENET2_TX_CLK__ECSPI4_MISO	0x100b1 /* from J16.6 */
			MX6UL_PAD_ENET2_TX_DATA1__ECSPI4_SCLK	0x100b1 /* from J16.2 */
			MX6UL_PAD_ENET2_RX_ER__GPIO2_IO15	0x100b1 /* from J16.4 */
		>;
	};
};

Note: The pins here were set arbitrarily. You should set them based on your hardware design, and make sure they are not conflicting with other devices in the device tree.
you can also have multiple chip selects.

6 Compile

Compile the kernel and device tree and update the SOM.

7 Testing

There's an SPI testing utility C code example in the kernel source tree: tools/spi/spidev_test.c (in older kernels: Documentation/spi/spidev_test.c)
To cross compile it use the following command:

$ $CC ./tools/spi/spidev_test.c -o ./spidev_test

On the target, for a test transmission, you can run the command

root@imx6ul-var-dart:~# spidev_test -D /dev/spidevM.N

where

  • M is the spi bus index (0 for ecspi1, 1 for ecspi2, ...)
  • N is the chip select index (0 for the 1st chipselect, 1 for the 2nd chipselect, ...)

For a test loopback, you can short MISO and MOSI pins and run

root@imx6ul-var-dart:~# echo "SPI test packet" > /tmp/SPI.in && echo "" > /tmp/SPI.out
root@imx6ul-var-dart:~# spidev_test -v -D /dev/spidevM.N-v -i /tmp/SPI.in -o /tmp/SPI.out

The SPI.in file will be used as test packet, sent over SPI, and the received bytes will be stored in the SPI.out file: SPI.in and SPI.out will match.