I2C not initiating unless pins.X.Y is called

[chalkers]

The following code on a cold boot doesn't initiate the I2C.

let smile: number[] = []
let meh: number[] = []
let frown: number[] = []
ht16k33.setAddress(HT16K33_I2C_ADDRESSES.ADD_0x70)
smile = [60, 66, 165, 129, 165, 153, 66, 60]
meh = [60, 66, 165, 129, 189, 129, 66, 60]
frown = [60, 66, 165, 129, 153, 165, 66, 60]
forever(function () {
    ht16k33.render(frown)
    pause(1000)
    ht16k33.render(meh)
    pause(1000)
    ht16k33.render(smile)
    pause(1000)
})

However if I add the following code I2C works...

let smile: number[] = []
let meh: number[] = []
let frown: number[] = []
/** HERE **/
pins.LED.digitalWrite(false)
ht16k33.setAddress(HT16K33_I2C_ADDRESSES.ADD_0x70)
smile = [60, 66, 165, 129, 165, 153, 66, 60]
meh = [60, 66, 165, 129, 189, 129, 66, 60]
frown = [60, 66, 165, 129, 153, 165, 66, 60]
forever(function () {
    ht16k33.render(frown)
    pause(1000)
    ht16k33.render(meh)
    pause(1000)
    ht16k33.render(smile)
    pause(1000)
})

Or even just setting the pull on the pins....

let smile: number[] = []
let meh: number[] = []
let frown: number[] = []
/** HERE **/
pins.SDA.setPull(PinPullMode.PullNone)
pins.SCL.setPull(PinPullMode.PullNone)
ht16k33.setAddress(HT16K33_I2C_ADDRESSES.ADD_0x70)
smile = [60, 66, 165, 129, 165, 153, 66, 60]
meh = [60, 66, 165, 129, 189, 129, 66, 60]
frown = [60, 66, 165, 129, 153, 165, 66, 60]
forever(function () {
    ht16k33.render(frown)
    pause(1000)
    ht16k33.render(meh)
    pause(1000)
    ht16k33.render(smile)
    pause(1000)
})

I don't need do set both but I just did as a test.

[chalkers]

I have two trinket m0 that I'm testing right now. One works fine, the other works only sometimes after multiple resets and different pause times at the between the beginning and setAddress calls. But it tends not to work on a cold boot.

[chalkers]

OK, another test on the one doesn't work...

I drop adafruit-circuitpython-trinket_m0-3.1.1.uf2 on the board, double tap to reset then drop the firmware from MakeCode that I wrote above, then the I2C device works. Unplug and then connect to an external power supply for cold boot and it doesn't work.

So whatever initializes the board with circuitpython enables i2c to work on the board that isn't working...

[jamesadevine]

Thanks @chalkers, great investigation, will reproduce and work out a fix (which from your great diagnostics will be simple 😄).

[pelikhan]

This call returns ERR_DENIED

    ret = i2c_m_sync_init(&i2c, i2c_sercom);

[jamesadevine]

@pelikhan it returns that if the I2C is already enabled (from reading the code)

[pelikhan]

I've added tracing and this is first time in the execution we try to mount i2c.

[pelikhan]

It looks like we are clashing with mounting a SPI for neopixels on Pad5.

[pelikhan]

@chalkers how I do repro your issue?

[chalkers]

Sorry, I've been in the middle of a move. If I recall correctly, I2C doesn't work on a "cold boot" i.e. after it's been removed from the computer and plugged in to an external source. The only way I've been able to guarantee it to work is to use:

pins.LED.digitalWrite(false)

or

pins.SDA.setPull(PinPullMode.PullNone)
pins.SCL.setPull(PinPullMode.PullNone)

I haven't unpacked all my electronics stuff yet but that is what I can remember.