← The Reserve
Barrel ESP32 pinout
The 30-pin USB-C "ESP-32S" board running device firmware 0.20.x with the barrel feature on. The same pins
are used on all 8 barrels.
Hold the board chip side up, USB at the bottom. The readers go on the LEFT header (the
one with VIN at the bottom). The BrightSign and the staff button go on the RIGHT header (3V3 at the
bottom). On 2026-10-13 all three readers were dead because they were on the wrong side.
The board
5 V powerground
reader busreader select (one per reader)
BrightSign serialstaff button
EN
VP
VN
D34
D35
D32
D33SS reader 3
D25SS reader 2
D26SS reader 1
D27MISO (all readers)
D14MOSI (all readers)
D12leave EMPTY
D13SCK (all readers)
GNDreaders GND
VINreaders VCC (5 V)
antenna
end
ESP32
chip side up
USB
D23
D22
TX0don't use
RX0don't use
D21
D19
D18
D5
TX2→ BrightSign pin 3
RX2← BrightSign pin 11
D4staff button (other leg to GND)
D2
D15
GNDBrightSign pin 1 or 7 + button
3V3not used
Plugs: left [VIN, GND, D13, empty D12] + [D14, D27, D26, D25, D33]; right [TX2, RX2, D4].
Each NFC reader (PN532 "V3" board)
| Reader pin | Goes to ESP32 | Shared? |
|---|
| VCC | VIN (5 V) | all 3 readers |
| GND | GND (left header, next to VIN) | all 3 readers |
| SCK | D13 | all 3 readers |
| MOSI | D14 | all 3 readers |
| MISO | D27 | all 3 readers |
| SS | reader 1 → D26 · reader 2 → D25 · reader 3 → D33 | one wire each |
Mode switch on every reader: 1 OFF, 2 ON (that's SPI). From the factory both are OFF (serial
mode), and in that mode the reader never answers on these wires. The reader only reads the switch at power-up,
so after changing it, unplug the power for 10 s.
Reader 1/2/3 = bottle position 1/2/3. The barrel doesn't care which bottle goes where.
BrightSign HD223 (12-pin GPIO connector)
Two 6-pin terminal blocks side by side. Count from the left facing the "GPIO" label: pins 1-6 are on the left block,
7-12 on the right block.
1GND
23.3V OUT
3RX ← TX2
4
5
6
left block
7GND
83.3V OUT
9
10
11TX → RX2
12
right block
| ESP32 | BrightSign |
|---|
| TX2 | pin 3 (3rd from the left, left block) |
| RX2 | pin 11 (5th from the left, right block) |
| GND | pin 1 or pin 7 |
Never connect pins 2 or 8: they are the BrightSign's own 3.3 V output. Pins 9/10 are a second serial
port the HD223 doesn't support, so leave them empty. Serial needs BrightSign OS 9.1 or newer, and the barrel card
carries the update file (it only installs on an older player). Source: BrightSign roControlPort docs
(EnableAlternateFunction(0/6, "serial1")).
Quick checks
- Tablet → Barrels → Wiring check. "all OK: 3 readers answer" = good. A line starting with "problem:"
names the wire to look at.
- Beep test, power OFF: meter on continuity, from each reader pin to its ESP32 pin in the table above.
This doesn't depend on any firmware.
- Power ON: each reader's VCC to GND should read about 5 V. Black probe on GND, red on 3V3 should read
+3.3; a minus sign means the black probe is on the wrong pin.
- BrightSign link: the Barrels page shows "video player" OK within a few seconds. If it never connects,
pins 3 and 11 are probably swapped.
Source of truth: platform/tools/device/BARREL.md (device firmware
0.20.x) and platform/tools/reserve_station_esp32/README.md. Updated 2026-10-13.