Can't get tcmenu with i2c rotary encoder to work on xiao samd21 (seeeduino) expansion board with ssd1306 oled

[AtmosphEng]

Not sure if this is a bug, so I'm posting this here.
I've recently used the xiao samd21 (seeeduino) with expansion board for a MIDI project, and now I'm trying to get tcmenu display on the ssd1306 oled and control via a single rotary encoder. I'm using the latest tcmenuDesigner and everything works fine if I use local pins for the rotary encoder i.e. on pins 9, 8, and 10. However when I try to use a PCF8575 i2c expander for the rotary encoder pins i.e. on expander pins 1, 2, and 0, then the display is initialised ok but there is no control (either up/down or button) from the i2c rotary encoder.
I've tested the i2c expander hardware setup is working ok, as it works with all the example code of the Github library Adafruit_PCF8575 - including interrupts via xiao samd21 pin 2.

I've uploaded my currently failing simple tcmenu with PCF8575 i2c rotary encoder test code at :
https://github.com/AtmosphEng/xiao-samd21-tcmenu-i2c-pcf8575-rotaryencoder-test

Could you please have a look and suggest some areas to check to try and get the expected normal operation with an i2c rotary encoder.
Thanks.

[davetcc]

Not saying this is a long term solution but, I see it is set to not poll (interrupt only) in code generator, could you please try changing the setting to polling to see if that works. Then we can rule out problems with interrupts.

[AtmosphEng]

Thanks. I already tried all polling options I could find but did not see any change or improvement. Maybe something else?

[davetcc]

I would start maybe seeing if this sketch works:https://github.com/TcMenu/IoAbstraction/blob/main/examples/interruptSwitchEncoder8574/interruptSwitchEncoder8574.ino if you change the PCF8574IoAbstraction to PCF8575IoAbstraction IIRC. This should be a more minimal test and debug if it works at all.

I've just run more or less a full suite of tests that included I2C expander support, and it was certainly working OK with a MCP23017 but I noticed that I no longer have a test for 8574, I'll set up another board that uses the 8574 as well (I have one of those chips). However, the 8575 was community provided, and I honestly don't even have the chip to hand.

If you can try the more basic example and see what gets logged, that would help to work out if there is an issue with the expander, in which case I may have to buy one and try it myself.

[davetcc]

I’ve ordered a breakout board that should arrive this weekend. I should have one for testing anyway.

[AtmosphEng]

Thanks. In interruptSwitchEncoder8574.ino, I changed the PCF8574IoAbstraction to PCF8575IoAbstraction but it would not compile. Then I did a find and replace of io8574 to 8574 but it also did not compile.

I also tried the io expansion chip MCP23017 you mentioned (with interrupts and polling) with my previous test code but I did not see any change or improvement. I also checked the MCP23017 hardware with the Adafruit-MCP23017-Arduino-Library and its blink sketch worked ok.

Maybe its something to do with the xiao expansion board which has two other onboard i2c devices 1) SSD1606 OLED at addr 0x3c, and 2) an RTC PCF8563T at addr 0x51. Sorry, but I don't have much experience with I2C devices, but since the xiao boards only have 14 pins in total, so it really needs an IO expansion chip for a rotary encoder.

[davetcc]

I have a Seeed MG126 board with an I2C mcp23017 expander attached to it. I also have a MEGA with multiple i2c devices attached. These were tested last week with respective menu sketches. Anyways, I’ve ordered a pcf8575 board and will try and test it myself to know it works for sure.

[AtmosphEng]

A question comes to mind. In tcmenuDesigner when specifying the encoder pins for PinA, PinB, and PinOK, with a 16-bit IO expander with A and B Ports e.g. is Port A pin 6 specified as 6 or A6 or something else?

[davetcc]

They start at 0 through to 15.