array-gpio breaks I2C on Pi Zero W

[dkossman]

Not sure if there is something else i need to do to make this work, but using array-gpio seems to break I2C.

Configuration: Pi Zero W running latest raspberry pi OS, two I2C devices connected (OLED display and an EZO pH circuit) to the standard SDA and SCL pins (3,5).

$ uname -a
Linux neonpi 6.6.74+rpt-rpi-v6 #1 Raspbian 1:6.6.74-1+rpt1 (2025-01-27) armv6l GNU/Linux

1. reboot the Pi
2. run i2cdetect -y 1
   -> normal output, both devices detected
3. run this node app:

const gpio = require("array-gpio")

// initialize gpio pins for relays - outputs, pullups, off
const r1 = gpio.setOutput(11);
const r2 = gpio.setOutput(13);
r1.off();
r2.off();

// returns a specific relay's state
//   input is a number (1 or 2)
function getRelay(relay) {
    if (relay == 1)
       return(r1.isOn);
    else if (relay == 2)
       return(r2.isOn);
    else
       return(-1) 
}

// set a specific relay's state
//   relay is 1 or 2
//   level is 0 or 1 (off or on)
function setRelay(relay, level) {
    if (relay == 1)
       (level) ? r1.on() : r1.off();
    else if (relay == 2)
       (level) ? r2.on(): r2.off();
}

console.log("relay 1: ", getRelay(1));
console.log("relay 2: ", getRelay(2));
setRelay(2, 1);
console.log("relay 2: ", getRelay(2));
setRelay(2, 0);
console.log("relay 2: ", getRelay(2));

--> This works as expected, but...

4. now re-run i2cdetect -y 1
   --> it fails to work correctly, output of the i2c map is extremely slow, and mangled. no I2C devices are detected. applications that try to write to the I2C bus fail with write errors
   --> it is necessary to power off and power back on the Pi to correct the problem

[EdAlegrid]

On the old version, it's possible the array-gpio may interfere with i2c detect since all peripheral registers are pre-loaded in the memory during startup.

On the latest version, each peripheral register will be mapped only in memory based on demand. So if you are just using gpio, then only the gpio registers will be mapped in the memory while the rest i2c, spi and pwm are not.
It should not interfere anymore.

[dkossman]

thanks for the update - i just re-tested with the current version and unfortunately i see the same problem as before :-(.
I'm running node 20.7.0 and debian bookworm on a Pi Zero W, with the latest package updates.
uname -a: Linux neonpi 6.6.74+rpt-rpi-v6 #1 Raspbian 1:6.6.74-1+rpt1 (2025-01-27) armv6l GNU/Linux

[EdAlegrid]

Just to clarify. I have tested the latest version on my end w/o i2c function it does not break or interfere w/ i2cdetect tool.

It seems to me you have another i2c application that runs in the background triggered or started by your array-gpio app.
You don't need to run i2cdetect while another i2c application is already running. They will interact with each other as expected since they are competing for the same i2c resources in your pi zero.

So your problem is not really an issue. Just run i2cdetect to confirm your i2c connections and addresses.
Don't re-run it when another i2c applications is already running.