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Drogheda/03-Architecture-Hardware/watchdog-protoboard-bringup.md

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tags project author date status
project-drogheda
hardware
watchdog
prototype
breadboard
bom
bring-up
Project Drogheda Helgen CTO 2026-06-22 Active — shop list for the Blackpill bring-up

Watchdog Bring‑up — Protoboard Shopping List (print me)

⚠ SUPERSEDED for sensors (2026-07-03): the proto suite is now AHT10 (0x38, alone on I²C1, 3V3) + LM35→PA7 + NTC→PB1 — no SHT40/SHT31/BME280/TMP102 on the proto (PCB-only). Charge cutoff = PA8 CHRG_RUN on the TP4056 IN+ (the kit module has no TEMP pin). Current shop lists = watchdog-protoboard-BOM-3boards.xlsx / watchdog-LISTA-DE-COMPRAS-ES.xlsx; wiring = ledger xlsx + Guía v2.2. The sensor/substitute rows below are kept for history only.

Goal: breadboard the v2.2 watchdog on your existing Blackpill, prove the state machine + sensing + load switch + fans + temp loop, before any PCB. All parts are through‑hole / breadboard‑friendly and stocked at a normal MX electronics shop (Steren / AG Electrónica / local). Quantities include spares. Pin map: 03-Architecture-Hardware/watchdog-pcb-v3-design#2 · firmware: blackpillrtkcode_v2.ino (v2.2).

0. Already have — do NOT buy

STM32F411 Blackpill · USB‑C/micro cable · 18650 + PowerBoost · Mean Well SD‑15B‑05 (or a bench PSU) · multimeter · the F9P + 4G master (only needed later, not for the bring‑up). A heat source (hair dryer / lighter / hot water cup) to trigger the thermal/fan test — household, no need to buy.

1. Core — bring up the "brains" (buy this even if the shop is sparse)

# Item Qty Value / part ~MXN For
1 Breadboard 830‑pt 2 half/full 120 build surface (2 = room for fans/sensors)
2 Jumper wires M‑M 1 pk 65 pcs 60 board wiring
3 Jumper wires M‑F 1 pk 40 pcs 50 to Blackpill / modules
4 Resistor assortment box 1 ¼ W (incl. 330Ω,1k,4.7k,10k,100k,220Ω) 120 dividers, gates, pull‑ups
5 LED (any) 5 3/5 mm 10 status LED on PB0
6 Ceramic cap 100 nF 10 0.1 µF (104) 20 ADC filters + decoupling
7 Electrolytic 100 µF / ≥16 V 4 — 20 rail bulk / modem‑burst reservoir
8 2N3904 (NPN, TO‑92) 3 load‑switch driver 15 PA1 → P‑FET gate
9 IRF9540 / IRF9540N (P‑MOSFET, TO‑220) 2 high‑side 5 V switch 40 switched 5 V to "stack"
10 10 kΩ trim pot 2 breadboard trimmer 30 sweep VBAT / ignition to test thresholds
11 Tactile button or slide switch 2 — 20 simulate ignition on/off
12 Male header strip 1 1×40, 2.54 mm 15 solder onto any module that needs pins

Core subtotal ≈ 520 MXN. With this you can flash v2.2, watch the $PHLG/TLM log, and validate the load switch + the three sense dividers + LED — the whole watchdog logic — without the thermal parts.

2. Thermal add‑ons — fans + temperature (the v3 new stuff)

# Item Qty Value / part ~MXN For / note
13 5 V fan, 40–60 mm, 3‑wire 1 3‑wire = has tach 60 one extraction fan; 3‑wire so PB10 reads RPM. Grab a 2nd as a spare if cheap
14 IRLZ44N (logic‑level N‑MOSFET, TO‑220) 2 fan low‑side PWM 30 1 + spare; must be logic‑level; see substitute below
15 Schottky 1N5819 3 fan flyback 10 one across the fan (1N4007 ok if out)
16 I²C temp+RH breakout 1 SHT31 / SHT40 ideal 120 matches firmware (0x44). RH catches condensation
17 Analog temp LM35 (TO‑92) 2 sure‑thing fallback 25 every shop has it; heat it → watch fans ramp
18 DS18B20 waterproof probe 1 1‑wire 45 great as the battery/modem hot‑spot probe
19 LM2596 buck module (adj.) 1 24/12 → 5 V 35 dedicated fan 5 V rail (caveat §0a) if no 2nd bench PSU

Thermal subtotal ≈ 260 MXN (one fan + driver + one temp option). Grab #13–15 for the fan, and one temperature option (#16 ideal, else #17/#18).

3. Substitutions (shop stock varies — these all work)

If they're out of… Buy instead Catch
IRLZ44N (logic‑level FET) 2N2222A (TO‑92) or TIP120 (Darlington) BJT: add 1 kΩ base resistor; fine for a <0.5 A fan. Plain IRF540/IRFZ44 won't fully turn on from 3.3 V — avoid.
SHT31/SHT40 I²C breakout BME280/BMP280 (I²C, common) address 0x76/0x77 → small firmware change
Any I²C sensor LM35 (analog) or DS18B20 (1‑wire) not I²C → firmware reads ADC / 1‑wire instead (I'll patch it)
IRF9540 P‑MOSFET keep your original, or 2N2222 high‑side is awkward — ask for any P‑channel ≥30 V gate fully pulled to GND by the 2N3904, so a standard P‑FET is OK here
1N5819 Schottky 1N4007 slightly slower; fine at fan PWM

4. Bring‑up order (so the list maps to actions)

  1. Just USB — flash v2.2, open serial @115200. Confirm BOOT/COLS/TLM lines and a $PHLG,...*CS every 30 s. (No external parts — this proves the firmware.)
  2. LED on PB0 via 330 Ω → watch the blink codes change with state.
  3. Load switch — 2N3904 + IRF9540 + 1 kΩ (base) + 10 kΩ (gate pull‑up) from a 5 V rail; put an LED+330 Ω on the switched output. Toggle: confirm OFF at reset, ON when PA1 drives. (This is the heart of recovery.)
  4. Sense dividers — two 10 kΩ each (÷2) into PA0 (battery via 18650) and PA4 (5 V rail); a 10 kΩ pot into PA5 (ignition). Sweep them and watch veh/ign flip in the TLM with hysteresis/debounce.
  5. Fan — PA6 → gate (220 Ω) of IRLZ44N → fan(−); flyback diode across the fan; 100 kΩ gate→GND. Watch it spin/ramp; tach wire → 10 kΩ pull‑up to 3V3 → PB10 → RPM in the log; unplug the fan → FAN_FAULT.
  6. Temperature — I²C breakout on PB6/PB7 (+4.7 kΩ pull‑ups), or LM35 on an ADC pin. Heat it → fans ramp per the 45→70 °C curve; at 75 °C the existing thermal derate kicks in.

5. Wiring cheat‑sheet (Blackpill side)

PA0  ← BAT  ÷2 (10k/10k) from 18650+        PA6  → 220Ω → IRLZ44N gate; fan(−); 1N5819 ∥ fan
PA4  ← 5V   ÷2 (10k/10k) from 5V rail        PB10 ← fan tach, 10k pull-up → 3V3 (1k series)
PA5  ← IGN  ÷2 (10k/10k) from pot/switch     PB6/PB7 → I²C SCL/SDA (+4.7k each → 3V3)
PA1  → 1k → 2N3904 base; collector → IRF9540 PB0  → 330Ω → LED → GND
        gate; 10k gate→5V; drain → switched   (PA7/PB12 left free — 2nd fan if ever needed)
        5V → stack (use an LED load to test)
GND/5V/3V3 rails common; fan 5V from a SEPARATE 5V (LM2596 or 2nd PSU) — not the stack rail.

6. Note on the temp sensor + firmware

The v2.2 firmware reads I²C SHT40 (0x44) + TMP102 (0x48). Whatever you bring back:

  • SHT31/SHT40 → works as‑is (SHT40) or a 1‑line address tweak (SHT31).
  • BME280 → change address + read call.
  • LM35 / DS18B20 → analog / 1‑wire; tell me which and I'll patch buildPHLG() + the fan‑curve input to read it. For tomorrow's bring‑up the fan loop can also be driven off the MCU‑internal temp (already in firmware) — heat the whole board and the derate still triggers, so you can prove the fan path even before the sensor arrives.

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