25 sensors
5 rows × 5 columns
pins (`see SparkFun`_)::
14
23
1. phototransistor collector, to pull-up for row
2. phototransistor emitter, to ground for column
3. led anode, to limiter for row
4. led cathode, to ground for column
so…
::
aM aN aO aP aQ cM cN cO cP cQ
14 14 14 14 14 14 14 14 14 14 …
23 23 23 23 23 23 23 23 23 23 …
Mb Nb Ob Pb Qb Md Nd Od Pd Qd
/---------- input1
a -+-10kΩ--+- output1
b ---220Ω--/
/---------- input2
c -+-10kΩ--+- output2
d ---220Ω--/
…
…
M ------------ output6
N ------------ output7
O ------------ output8
P ------------ output9
Q ------------ output10
row outputs: 05 23 19 18 26
col outputs: 34 33 35 21 22
adc inputs: 02 04 tdi/12 27 tms/14 (adc2 2 0 5 7 6)
amp: 25 (dac1) 32 (enable)
amplifier
https://learn.adafruit.com/stereo-3-7w-class-d-audio-amplifier/assembly
https://forum.arduino.cc/index.php?topic=269972.0
https://www.hackster.io/julianfschroeter/stream-your-audio-on-the-esp32-2e4661