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lkd:laboratoare:04 [2024/07/11 15:15] daniel.baluta |
lkd:laboratoare:04 [2024/07/11 16:42] (current) daniel.baluta [Presentation] |
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| ==== Presentation ==== | ==== Presentation ==== | ||
| - | * follow slides at {{:lkd:laboratoare:lkd_slides_03.pptx| Session 3}} | + | * no slides, all practical |
| ==== Practical lab ==== | ==== Practical lab ==== | ||
| Line 11: | Line 10: | ||
| === Exercise 1 === | === Exercise 1 === | ||
| + | |||
| + | == Step 1 - Create the hardware setup == | ||
| Enable I2C proximity sensor [[https://www.optimusdigital.ro/en/index.php?controller=attachment&id_attachment=4892 | vl53l]]. | Enable I2C proximity sensor [[https://www.optimusdigital.ro/en/index.php?controller=attachment&id_attachment=4892 | vl53l]]. | ||
| - | Identify GND, VCC, I2C_SCL and I2C_SDA data lines on expansion header and connect the sensor accordingly. | + | Connect GND, VCC(3V), I2C3_SCL_3V3 and I2C3_SDA_3V3 data lines on expansion header and connect the sensor accordingly. |
| {{:lkd:laboratoare:expansion_1.png}}. | {{:lkd:laboratoare:expansion_1.png}}. | ||
| + | |||
| + | Setup should look like this: | ||
| + | |||
| + | {{:lkd:laboratoare:setup1.jpeg?500}}. | ||
| + | |||
| + | == Step 2 - Find a proper Linux kernel driver == | ||
| + | |||
| + | Look inside ''~/work/nss-linux/drivers/iio'' and find a proper driver for ''vl53l'' sensor. Use ''git grep vl53l''. Once you find the correct source file look inside the driver and remember the compatible string. | ||
| + | |||
| + | Once you found the driver, use ''make menuconfig'' and select it to be compiled as a module. ''<M>'' | ||
| + | |||
| + | == Step 3 - Create a proper device tree node == | ||
| + | |||
| + | Look inside ''arch/arm64/boot/dts/freescale/imx8mq-pico-pi.dts'' and add your node under ''i2c3'' node. | ||
| + | |||
| + | Your node should look like this: | ||
| + | |||
| + | <code c> | ||
| + | &i2c3 { | ||
| + | proximity-sensor@XX { | ||
| + | compatible = <compatible-you-found-in-the-driver>; | ||
| + | reg =<XX>; | ||
| + | pinctrl-0 = <&pinctrl_prox>; | ||
| + | status = "okay"; | ||
| + | }; | ||
| + | }; | ||
| + | </code> | ||
| + | |||
| + | XX - is the address of the I2C device. There are two ways of finding this. You can dig inside the [[https://www.optimusdigital.ro/en/index.php?controller=attachment&id_attachment=4892 | datasheet ]] and confirm the address by scanning for devices on i2c3 node on the hardware. Use ''i2cdetect -y 2''. | ||
| + | |||
| + | The datasheet states that the I2C address is as shown as below, but you need to look closer and also understand the output of i2c scan command ''i2cdetect -y 2''. | ||
| + | |||
| + | {{:lkd:laboratoare:i2caddr.png}} | ||
| + | |||
| + | == Step 4 - Load the driver & read the distance measured by sensor == | ||
| + | |||
| + | Once the device tree is ready, recompile the kernel and boot the board. On the board, use ''modprobe <driver-name>'' to load the driver. If everything goes well the driver will be correctly loaded and you will be able to read data. | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ modprobe vl53l0x-i2c | ||
| + | $ cat /sys/bus/iio/devices/iio:device0/in_distance_scale | ||
| + | </code> | ||
| + | |||
| + | Use the following script the poll for proximity measurements every 0.5 seconds: | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ cat read_meas.sh | ||
| + | |||
| + | while true; do | ||
| + | cat /sys/bus/iio/devices/iio:device0/in_distance_raw | ||
| + | sleep 0.5 | ||
| + | done | ||
| + | |||
| + | </code> | ||
| + | |||
| + | |||
| + | === Exercise 2 === | ||
| + | |||
| + | Control a motor using GPIOs. Use the following {{:lkd:laboratoare:motorcontrolsetup.pdf| Guide }} | ||
| + | |||
| + | {{:lkd:laboratoare:motor1.jpeg?500}} | ||
| + | |||
