# This describes how to use GPIO pins````
#
#

Follow wiring guide from sparkfun
Dont install python
    install nodejs and npm instead
then install
    npm i -g onoff
Enable i2c
    https://github.com/fivdi/i2c-bus/blob/master/doc/raspberry-pi-i2c.md

New boot config, when also enabling pull-up for GPIO17 and 27:
````
    # See /boot/overlays/README for all available options
    dtparam=i2c_arm=on
    dtparam=audio=on
    gpio=17=pu
    gpio=27=pu

    dtoverlay=vc4-kms-v3d
    dtparam=krnbt=on
    initramfs initramfs-linux.img followkernel
````

Using it in as NodeJS project to control amp volume using up/down buttons:
````
    const i2c = require('i2c-bus');
    const Gpio = require('onoff').Gpio;

    const MAX9744_ADDR = 0x4B;

    let curVolume = 20;

    async function setVolume(v){
    const bus = await i2c.openPromisified(1);
    const wbuf = Buffer.from([v]);
    bus.i2cWrite(MAX9744_ADDR,wbuf.length,wbuf);
    bus.close()
    }

    setVolume(30);

    const upButton = new Gpio(17, 'in', 'both', {activeLow: true});
    const downButton = new Gpio(27, 'in', 'both', {activeLow: true});

    upButton.watch((err,value) => {
    if(value && curVolume < 63){
    console.log('UP');
    setVolume(++curVolume);
    }
    });
    downButton.watch((err,value) => {
    if(value && curVolume > 0){
    console.log('DOWN');
    setVolume(--curVolume);
    }
    });

    console.log("Watching");
````