Board and Connectors

The unit has a single PCB, silkscreened QT20P2_V6.3 and dated 2023-07-22 (PCB revision 6.3). Components are on both sides. This page is taken from the silkscreen labels; items marked inferred are reasoned from the labels and the signal names and have not been measured.

Annotated photos

Front side (LEDs, button, connectors)

#	Item
1	LED1 to LED4
2	LED driver transistors Q3 to Q6 and their resistors
3	Front tact switch SW1
4	BOOT jumper pads
5	JP2 connector: OUTA, OUTB, GND, PIP, KEY
6	EMV connector: OUTA1, OUTB1
7	KW connector (blue): KEY2, GND
8	BAT connector (red): -, +
9	Board marking QT20P2_V6.3, 2023-07-22

Module side (ESP32 module, power, drivers)

#	Item
1	Battery pads BAT+, BAT-
2	D1 diode at the battery input
3	KEY2 and GND pads (the blue KW connector on the front)
4	KEY1, PIP, GND1, OUTB, OUTA pads (the JP2 connector on the front)
5	OUTA1, OUTB1 pads (the EMV connector on the front)
6	U1 driver IC with the 1 ohm shunt R20
7	U3 driver IC
8	Driver input test pads INA, INB, INA1, INB1
9	BAT_ADC and ADC_CUR test pads
10	U2 DC-DC converter and its inductor
11	JP1 UART pads: VDD, GND, TXD, RXD
12	BOOT pads (the same through-holes as the BOOT jumper on the front)
13	U4, the ESP32-S2-SOLO module (MBN4, 4 MB flash)

The connectors on the front are through-hole parts, so each connector pin shows up on the module side as a pad with the same signal name. The module side is mirrored relative to the front.

Connectors (front side)

Connector	Pins	Notes
JP2 (5-pin, white)	OUTA, OUTB, GND, PIP, KEY	OUTA/OUTB are a driver output pair; PIP and KEY are inputs from the connector (roles unconfirmed)
EMV (2-pin, white)	OUTA1, OUTB1	second driver output pair; "EMV" is probably the solenoid valve (French "electrovanne"), inferred
KW (2-pin, blue)	KEY2, GND	a second external switch input (role unconfirmed)
BAT (2-pin, red)	-, +	battery

The module side also has test pads INA, INB, INA1, INB1 (driver inputs) and ADC_CUR, BAT_ADC (analog sense points).

Programming and debug access

• JP1 (module side): four pads labeled VDD, GND, TXD, RXD. This is the UART access (3.3 V logic).
• BOOT pads: a two-pad jumper marked BOOT at the top right of the front side; the same two through-holes show on the module side. Shorting it at power-up is the usual way to enter the ROM download mode (inferred, standard for this chip).

Check for solder bridges between the JP1 pads before powering.

Likely hardware roles

Outputs	GPIO	Probable role
four outputs	GPIO40, 39, 41, 42	the four LEDs through Q3 to Q6 (inferred: four outputs, four LED transistors)
two outputs	GPIO9, GPIO10	one driver IC's input pair (valve), see Hardware GPIO Map
two outputs	GPIO15, GPIO2	probably the other driver IC's input pair (inferred)

The two driver ICs (U1 and U3) match the two valve variants, and the ADC_CUR shunt suggests motor-current sensing (possibly the valve feedback). None of this is measured yet.

See Flashing and Recovery and Open Tasks.