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I2C lines pulled to 5v instead of 3.3v #3

Closed jdbaptista closed 2 months ago

jdbaptista commented 2 months ago

Currently, the I2C lines are pulled up to 5v, which I don't think the esp32 GPIO lines can handle. The matrix driver ICs can operate anywhere from 2.7-5.5v on data input lines when Vcc = 5v, so I think we can just change the 5v pullup to 3.3v.

Also, the resistors on the matrix driver data lines don't match the typical application circuit in the datasheet and are duplicated (present in matrix 1,2,3) for the shared SDA and SCL lines; I think they should be present only once.

I'm writing this as an issue instead of just making a commit because I don't want to break anything that was done intentionally. Any feedback before I make the change?

aidan-9880 commented 2 months ago

They should be pulled to 3.3v, that's my mistake. Used the wrong power symbol on accident. The resistor values and number of them is fine, 3 4.7k ohm in parallel = about 1600 ohms, around where it needs to be according to https://www.ti.com/lit/an/slva689/slva689.pdf (page 3). The i2c tracks are relatively long = high capacitance, so I didn't want to go too high.

I have also made a few minor changes since I uploaded those files, will update the kicad files tomorrow with the final version when I'm in the office.

aidan-9880 commented 2 months ago

Switched to one 2k ohm resistor on each I2C line, pulled to 3.3v. Also pulled the other LED driver resistors (on interrupt and shutdown pins) to 3.3v.