Support I2C IO Expanders? (MCP23017)

[blazini36]

When I was first testing this, I made a break-out board for an Arduino Mega. I designed a 32key Matrix key panel with LEDs at the same time. When I got that working with Arduino connector, I was not happy with the pulsing effect of the LEDs. I also had pretty bad lag (which seems it may have been resolved with adjusting the serial timeout recently)

I made another break out board using a Teensy 4.1 which is also arduino compatible but much faster. I figured this may resolve the lag issues. The Teensy 4.1 has far fewer IO pins than the Mega so I used 1 MCP23017 IO expander on the break out board and I remade the key panel using 4 MCP23017s meant to connect to a separate I2C channel than the 1 on the BOB.

I was going to get help adding the code for this from a friend (I don't really do code myself), when I realized the lag was still too bad to deal with I basically just dropped the whole thing. Now that I see there may be an easy fix for the lag issue I am wondering if there is any chance someone will add the support for I2C IO expanders to this code. I'd like to give this a try again but since I already have a Teensy BOB and boards that use I2C IO expanders, I would prefer to use that.

[blazini36]

Just in case anyone is considering adding this feature, I have tested this code to work with my key panel with a Mega 2650. It's just an expansion of the example code since I barely know what I'm doing but it does work perfectly with the key panel I made to this schematic.

I2C_Key_panel.pdf

an Interrupt line is present but not used in this example. Maybe this will take some of the burden off the person who might be willing to add the code to Arduino Connector.

CNC_ControlPanel_I2C_Keypad_Test1.txt