part,value,holes,note
"Pico 2W","2 × 20-pin female header","A13–T13 and A20–T20 (pins 1–20 down the left, 40–21 down the right)","USB end flush with the top edge of the board, past strip A"
"U1","6N137","U5–X5, U8–X8","6N137 in a DIP-8 socket. Notch toward strip U, pin 1 at hole U5. Pin 7 (enable) is tied to pin 8 by the U10–V10 link."
"R1","220 Ω","V2 – Y2","MIDI IN current limit. 3-hole span: stand it upright, or use a small ⅛ W part flat. If learning ever misses notes, use 150 Ω."
"D1","1N4148","V4 – W4","Band (cathode) on V4, the opto LED anode side. Stands upright (1-hole span)."
"R2","1 kΩ","W10 – AB10","Opto output pull-up to 3.3 V"
"C1","100 nF","U11 – X11","6N137 supply bypass, right beside the chip: U11 is its 5 V (pin 8) strip, X11 its GND (pin 5) strip. Required. Fit it after the beep test."
"R4","10 Ω","X21 – X25","MIDI OUT KIT, TX line (RC). Lies flat along strip X, across the cut at X23 (4-hole span, ¼ W fits). SEED hangs right above it."
"R5","33 Ω ½ W","V19 – AB19","MIDI OUT KIT, 3.3 V line (RA). ½ W: a mono plug in the jack shorts it to ground."
"R6","10 Ω","U28 – Y28","MIDI OUT SYNTH, TX line (RC)"
"R7","33 Ω ½ W","V30 – AB30","MIDI OUT SYNTH, 3.3 V line (RA). ½ W, same reason as R5."
"Link","wire","A34 – Z34","5 V (VBUS) to the 5 V strip"
"Link","wire","E32 – AB32","3V3 to the 3V3 strip"
"Link","wire","R33 – AA33","GND to the GND strip"
"Link","wire","U13 – Z13","opto VCC to 5 V"
"Link","wire","U10 – V10","opto enable (pin 7) to VCC (pin 8): the 6N137 output only works with pin 7 high"
"Link","wire","X12 – AA12","opto GND to GND"
"Link","wire","W9 – B9","opto out to GP1 (MIDI RX), strip B"
"Link","wire","A15 – X15","GP0 (TX KIT) to strip X (R4), straight down under the Pico between its headers"
"Link","wire","F14 – Y14","GP4 (TX SYNTH) to strip Y (R6), straight down under the Pico between its headers"