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@ -4,8 +4,10 @@ This guide assumes you have a correctly installed and set up board, with the cor
*Caveat:* notes here are biased towards Python usage, since that is what I will be using in my projects. *Caveat:* notes here are biased towards Python usage, since that is what I will be using in my projects.
## Common ## Common
You need to install the GPIOd package to allow access to the raw GPIO devices:
``` ```
$ sudo apt install gpiod $ sudo apt install gpiod
$ sudo reboot
``` ```
## General Purpose GPIO (digital read/write) ## General Purpose GPIO (digital read/write)
@ -67,7 +69,7 @@ while true ; do
echo echo
done done
``` ```
See the [kernel guide](https://www.kernel.org/doc/html/latest/driver-api/pwm.html#using-pwms-with-the-sysfs-interface) for the parameters we set to assign and control the pin. See the [kernel PWM API guide](https://www.kernel.org/doc/html/latest/driver-api/pwm.html#using-pwms-with-the-sysfs-interface) for the parameters we set to assign and control the pin.
## I2C ## I2C
**Working**: I have read temperature, pressure and humidity from a BME280 sensor connected to pins `3` and `5`, and output that to a OLED display on the same bus. See the python example below. **Working**: I have read temperature, pressure and humidity from a BME280 sensor connected to pins `3` and `5`, and output that to a OLED display on the same bus. See the python example below.
@ -77,7 +79,8 @@ Install `i2c-tools` and add your user to the `i2c` group to access the device no
$ sudo apt install i2c-tools $ sudo apt install i2c-tools
$ sudo usermod -a -G i2c <username> $ sudo usermod -a -G i2c <username>
``` ```
Reboot at his point, after the reboot you should have devices in the `/dev` tree for i2c. Use `i2cdetect` to scan them for attached devices: Reboot at his point, after the reboot you should have devices in the `/dev` tree for i2c busses. Use `i2cdetect` to scan them for attached devices.
* Note that the i2c busses are numbered sequentially, not by their hardware number. The Device Tree I am using here has `I2C0` and `I2C3` enabled; but they are named `i2c-0` and `i2c-1` respectively in `/dev`.
```console ```console
$ ls -l /dev/i2c* $ ls -l /dev/i2c*
crw-rw---- 1 root i2c 89, 0 Sep 23 21:17 /dev/i2c-0 crw-rw---- 1 root i2c 89, 0 Sep 23 21:17 /dev/i2c-0
@ -96,20 +99,20 @@ $ i2cdetect -y 0
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- 76 -- 70: -- -- -- -- -- -- 76 --
``` ```
You can see that interface `0` has a BME280 device at address`0x76`, and a SSD1306 OLED screen at `0x3c`. You can see that interface `i2c-0` has a BME280 device at address`0x76`, and a SSD1306 OLED screen at `0x3c`.
## SPI ## SPI
**Working?**: When I enable SPI1 in the device tree a device is registered at `/sys/devices/platform/soc/4026000.spi/` **Working?**: When I enable SPI1 in the device tree a device is registered at `/sys/devices/platform/soc/4026000.spi/`
* It lists it's driver (correctly) as `sun6i-spi` and is a bus master. * It lists it's driver (correctly) as `sun6i-spi` and is a bus master.
* Kernel drivers that use SPI via `pinctl` should be able to use this. * Kernel drivers that use SPI via `pinctl` should be able to use this.
* But no block device appears at /dev/spi*. * But no block device appears at /dev/spi*.
* Normally spi-tools provides userland support via the /dev/spi* device. * Normally `spi-tools` provides userland support via the /dev/spi* device.
* I do not plan to use SPI so I have not tested further. * I do not plan to use SPI so I have not tested further.
--------------------------------------------------------- ---------------------------------------------------------
# Python demo # Python demo
The following is a demo of using I2C to read data from a BME280 Temperature, Humidity and Pressure sensor, and display ito on a SSD1306 OLED display. The following is a demo using I2C to read data from a BME280 environmental sensor, and display it on a SSD1306 OLED display.
- It will be expanded with lgpio PWM and pin input/interrupt code later. - It will be expanded with lgpio PWM and pin input/interrupt code later.
- All the install steps here (making the venv, `apt` and `pip`) are tediously slow on the MQ Pro. - All the install steps here (making the venv, `apt` and `pip`) are tediously slow on the MQ Pro.
@ -140,8 +143,7 @@ $ source env/bin/activate
This is my test setup; A bme280 and SSD1306 OLED on the I2C bus, a blue LED is on a PWM pin and a pushbutton on a free digital IO pin. The MQ Pro itself is hidden underneath the (blue) LoRa HAT. This is my test setup; A bme280 and SSD1306 OLED on the I2C bus, a blue LED is on a PWM pin and a pushbutton on a free digital IO pin. The MQ Pro itself is hidden underneath the (blue) LoRa HAT.
#### Work In Progress #### #### Work In Progress ####
Demo runs but still needs expanding to demo lgpio and pwm control The demo runs well, but still needs expanding with lgpio and pwm control
--------------------------------------------------------- ---------------------------------------------------------
@ -170,6 +172,8 @@ cpu_thermal-virtual-0
Adapter: Virtual device Adapter: Virtual device
temp1: +19.4°C temp1: +19.4°C
``` ```
**HOWEVER**: This is nonsense.. I'm testing with the board in an enclosure; and the attached BME280 sensor is showing room temp outside the enclosure as 22°C. **HOWEVER**: This is nonsense..
I'm testing with the board in an enclosure; and the attached BME280 sensor is showing room temp outside the enclosure as 22°C.
- The CPU is definately running hotter than 19° 🤦 - The CPU is definately running hotter than 19° 🤦
- ¿Check out the device tree, maybe a bad offset. Or some kind of calibration/reference voltage needed? - ¿Check out the device tree, maybe a bad offset. Or some kind of calibration/reference voltage needed?