Shift registers for switch matrix and LED matrix

Other Hardware LEDs and Multiplexing
1

I reverse engineered the PCB of a cheap mechanical full-size keyboard so that I can interface it with an ESP32-S3 but I don't have enough GPIOs for both matrices.

The matrices share the column pins.
The switch matrix is wired in 21 columns and 6 rows.
The LED matrix is wired in 22 columns and 6 rows (there is an extra column for the status LEDs) (rows = anode, columns = cathode).
The transistors on the LED matrix are all 2TY for the columns and for the rows (1 = Base, 2 = Emitter, 3 = Collector).

Which type of shift registers do I need for the switch matrix, and which type for the LED matrix? According to this website it seems that I should use the HC164 for the switches and the HC595 for the LEDs, is this correct?

2

Parallel to serial? All I know is 74HC165...

Read-32-Switches-Using-3-Arduino-Pins-768x439
Read-32-Switches-Using-3-Arduino-Pins-768x439768×439 39.1 KB

3

I bought a triple TM74HC595 module for this project, but I have multiple doubts about how to wire it to the keyboard's matrices.

  • Can the columns be wired to the output pins of the 74HC595? (rows directly to MCU)
  • If I use 5V for powering the LEDs, will it be safe to use a 3.3V microcontroller?

860×860 403 KB

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