https://github.com/lanefu/sbc-gpio-pcf857x

GPIO scripts and examples for linux, RPI alternatives using pcf8574 IO Expander
https://github.com/lanefu/sbc-gpio-pcf857x

Last synced: 17 days ago
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GPIO scripts and examples for linux, RPI alternatives using pcf8574 IO Expander

• Host: GitHub
• URL: https://github.com/lanefu/sbc-gpio-pcf857x
• Owner: lanefu
• Created: 2020-12-31T14:09:40.000Z (almost 4 years ago)
• Default Branch: main
• Last Pushed: 2021-11-27T13:29:11.000Z (almost 3 years ago)
• Last Synced: 2023-03-11T22:03:01.425Z (over 1 year ago)
• Language: Python
• Size: 6.02 MB
• Stars: 2
• Watchers: 2
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md

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README

        
# sbc-gpio-pcf857x

GPIO scripts and examples for linux / Armbian, RPI alternatives using i2c [pcf8574](https://www.ti.com/product/PCF8574) IO Expander found in cheap GPIO breakout boards.

## background

My personal use case was to make a uart and gpio control hat for a [Libre Computer Tritium H5](https://www.loverpi.com/collections/tritium) to control power for SBCs and collect consoles.

Because I wired relays to be normally closed.  Relay Off == power on, Relay On == power off.   My [shell library](lib/gpio.sh) functions reflect that use case.

![i2c and uart breakout hat](img/console_hat.jpg)

![my relay board for usb power](img/usb_relay.jpg)

## Getting Started

### prerequisites

* Be sure to enable your i2c bus in `armbian-config` and reboot

* install `i2c-utils` package

* Figure out your address of the io expander.. default is 0x38.  See resources below on how to confirm with i2cdetect, etc

### initialize

My gpio breakout board showed up as `gpio504` this means the gpio pin names are gpio504-gpio511

I added folllowing lines into my `/etc/rc.local` script to load kernel module and load driver for i2c and expander

```sh

modprobe gpio-pcf857x

echo pcf8574 0x38 > sys/bus/i2c/devices/i2c-0/new_device

```

### example - bash

requires running as root....

```sh

source lib/gpio.sh

demo

```

```sh

source lib/gpio.sh

gpio_init

gpio_show_all

gpio_set 505 value 1

gpio_show_all

sleep 1s

gpio_bounce 506

gpio_bounce 507

gpio_show_all

gpio_unexport_all

```

### example - python

Running on [Orange Pi PC](https://www.armbian.com/orange-pi-pc/); with 2 LEDs on gpio 12 and 13

```sh

sudo python3 lib/api.py -c /dev/gpiochip0 -l 12 13

```

Then, on the same device

```sh

curl localhost:5000/on

curl localhost:5000/off

```

Or form an other device on the same network

```sh

curl orangepipc.local:5000/12/toggle

curl orangepipc.local:5000/13/bounce

curl orangepipc.local:5000/toggle

curl -s orangepipc.local:5000/state | jq

```

```json

{

  "12": {

    "active": "high",

    "direction": "output",

    "value": 0

  },

  "13": {

    "active": "high",

    "direction": "output",

    "value": 1

  }

}

```

```sh

curl orangepipc.local:5000/13/toggle

curl -s orangepipc.local:5000/13/state | jq

```

```json

{

  "active": "high",

  "direction": "output",

  "value": 0

}

```

routes */gpio-num/#* impacts a single gpio while */#* impacts all configured lines

## resources

* https://www.ti.com/product/PCF8574

* https://elixir.bootlin.com/linux/v2.6.30/source/Documentation/i2c/chips/pcf8574

* https://github.com/torvalds/linux/blob/master/Documentation/i2c/old-module-parameters.rst

* https://www.waveshare.com/wiki/Raspberry_Pi_Tutorial_Series:_I2C

* [clicky demo video](https://www.youtube.com/watch?v=CRsYRhhzGEs)