ESP32 Body Controller

GitHub: Carputer-project/esp32_body_controller

TCP command server for body control — HVAC relays, door locks, windows, fan speed, remote start, and Kenwood radio I2C sniffer. Runs on Adafruit Feather ESP32.

Role

Creates the Carputer_ECU WiFi access point (192.168.4.1) and listens for TCP commands on port 5000. Controls all body electronics via ULN2003A relay drivers. Sniffs the Kenwood radio's I2C bus to capture volume knob changes.

Network

Parameter	Value
WiFi Mode	AP (Access Point)
AP SSID	Carputer_ECU
AP Password	12345678
AP IP / Gateway	192.168.4.1
Subnet	255.255.255.0
TCP server port	5000 (commands from carputer app)
Mesh UDP port	5010 (V2V mesh broadcast)
Status push interval	2000ms

Relay Wiring (via ULN2003A Darlington Arrays)

Two ULN2003A driver ICs handle all relay switching. ULN2003A provides open-collector outputs with built-in flyback diodes for inductive loads.

ULN2003A #1 — Body Relays

ESP32 GPIO	Function	Relay	Wire To	Notes
GPIO 25	Door Lock	LOCK relay	Coil+ to ULN2003A #1 pin 1	HIGH = locked
GPIO 26	Window Up	WIN_UP relay	Coil+ to ULN2003A #1 pin 2	Pulse 500ms HIGH then LOW
GPIO 27	Window Down	WIN_DN relay	Coil+ to ULN2003A #1 pin 3	Pulse 500ms HIGH then LOW
GPIO 32	Extra 1	EXTRA1 relay	Coil+ to ULN2003A #1 pin 4	Generic (interior light bridge)
GPIO 33	Extra 2	EXTRA2 relay	Coil+ to ULN2003A #1 pin 5	Door chime buzzer (pulse 200ms) / Siren

ULN2003A #2 — HVAC & Fan Relays

ESP32 GPIO	Function	Relay	Wire To	Notes
GPIO 2	HVAC Relay	HVAC relay	Coil+ to ULN2003A #2 pin 1	HIGH = HVAC on
GPIO 4	AC Relay	AC relay	Coil+ to ULN2003A #2 pin 2	HIGH = AC on
GPIO 5	Remote Start	RSTART relay	Coil+ to ULN2003A #2 pin 3	HIGH = remote start active
GPIO 18	Fan 1 Relay	FAN1 relay	Coil+ to ULN2003A #2 pin 4	Speed 1 = HIGH
GPIO 12	Fan 2 Relay	FAN2 relay	Coil+ to ULN2003A #2 pin 5	Speed 2 = HIGH

Fan speed logic:

Speed	GPIO 18 (FAN1)	GPIO 12 (FAN2)
0 (off)	LOW	LOW
1	HIGH	LOW
2	HIGH	HIGH

ULN2003A Wiring

ULN2003A Pin 1-7 (IN1-IN7) ← ESP32 GPIO (via 1KΩ series resistor recommended)
ULN2003A Pin 8 (GND) → Common GND
ULN2003A Pin 9 (COM) → +12V (relay coil supply)
ULN2003A Pin 10-16 (OUT1-OUT7) → Relay coil negative side
Relay coil positive side → +12V

Kenwood Radio (TEA6320T) — I2C Sniffer

ESP32 Pin	Wire To	Function
GPIO 21	TEA6320T SDA (pin 22 on TEA6320T)	I2C data — sniffer mode
GPIO 19	TEA6320T SCL (pin 21 on TEA6320T)	I2C clock — sniffer mode
GND	Radio chassis GND	Common ground

I2C Configuration:

• Address: 0x40 (7-bit), 0x80 (8-bit write)
• Bus speed (hybrid master): 50 kHz
• Sniffer: GPIO interrupt-driven, monitors MICOM writes to TEA6320T

TEA6320T Register Map

Reg	Address	Function	Range
VOLUME	0x00	Volume + Loudness	dB+43: -31dB(12) to +20dB(63). Bit 6: LOFF
FFR	0x01	Front-Right fader	0-15 (0=off)
FFL	0x02	Front-Left fader	0-15 (0=off)
FRR	0x03	Rear-Right fader	0-15 (0=off)
FRL	0x04	Rear-Left fader	0-15 (0=off)
BASS	0x05	Bass	0-31 (16=flat)
TREBLE	0x06	Treble	0-31 (16=flat)
SWITCH	0x07	Source + Mute	[GMU][X][X][X][X][SC2][SC1][SC0]

Source select (SC bits): 0=CD(A), 1=B, 2=AUX(C), 3=D, 4=E, 5=Mono

AUX Input C Wiring

Audio Source ──[1µF]──┬── TEA6320T pin 13 (L) / pin 20 (R)
│
[47kΩ]
│
GND

Hybrid Write Mode

ESP32 normally sniffs I2C via GPIO interrupts. When app sends radio command:

1. Disable ISR
2. Wire.begin(50kHz) — switch to master mode
3. Write register to TEA6320T (~20ms)
4. Wire.end() — release bus
5. Reconfigure GPIO as input with pullup
6. Re-enable ISR — resume sniffing

Knob Behavior

Knob Action	ESP32 Output	Carputer Effect
Turn right (vol up)	J:R + VOL:<dB>	Navigate right + media volume up
Turn left (vol down)	J:L + VOL:<dB>	Navigate left + media volume down
Push (select)	J:S	Select/enter (requires solder wire to GPIO13)

Joypad Inputs

ESP32 GPIO	Function	Type	Notes
GPIO 36	Joystick Y	Analog (ADC)	<1200=down, >2800=up, 250ms debounce
GPIO 39	Joystick X	Analog (ADC)	<1200=left, >2800=right, 250ms debounce
GPIO 22	SELECT button	INPUT_PULLUP	Active LOW
GPIO 23	EXIT button	INPUT_PULLUP	Active LOW
GPIO 13	Radio Knob Push	INPUT_PULLUP	Active LOW, sends J:S (solder wire required)

Available Free Pins

For future expansion (5-button joypad, sensors, etc.):

GPIO	Type	Notes
GPIO 14	INPUT_PULLUP	Best for buttons
GPIO 16	INPUT_PULLUP	Best for buttons
GPIO 17	INPUT_PULLUP	Best for buttons
GPIO 34	Input only	Needs external 10K pull-up to 3.3V
GPIO 35	Input only	Needs external 10K pull-up to 3.3V
GPIO 0	INPUT_PULLUP	Strapping pin (LOW at boot = download mode)

Command Protocol (TCP text)

Command	Action	Pin Used
H0/H1	HVAC off/on	GPIO 2
S0-S2	Fan speed	GPIO 18 + GPIO 12
A0/A1	AC off/on	GPIO 4
L0/L1	Unlock/lock	GPIO 25
W1	Window up (500ms pulse)	GPIO 26
W0	Window down (500ms pulse)	GPIO 27
R0/R1	Remote start off/on	GPIO 5
P10/P11	Extra 1 off/on	GPIO 32
P20/P21	Extra 2 off/on	GPIO 33
C	Chime (200ms pulse)	GPIO 33
K0-K4	Radio source	I2C → TEA6320T
V-31..V20	Radio volume (dB)	I2C → TEA6320T
M0/M1	Radio unmute/mute	I2C → TEA6320T
B0-B31	Bass (16=flat)	I2C → TEA6320T
T0-T31	Treble (16=flat)	I2C → TEA6320T
D-15..D15	Fader	I2C → TEA6320T
O0/O1	Loudness off/on	I2C → TEA6320T

JSON Commands (TCP)

{"cmd": "bind", "vin": "..."} // Bind module to VIN
{"cmd": "unbind"} // Unbind module
{"cmd": "arm"} // Arm alarm
{"cmd": "disarm"} // Disarm alarm
{"cmd": "remote_start"} // Remote start engine
{"cmd": "remote_stop"} // Remote stop engine
{"cmd": "lock"} // Lock doors
{"cmd": "unlock"} // Unlock doors

Status Response

H:0 S:0 A:0 L:0 R:0 F:0 P:0,0 K:0 V:0 M:1 B:16 T:16 D:0 O:0

Build & Flash

cd esp32_body_controller
pio run # Build
pio run --target upload # Upload via USB
pio device monitor -b 115200 # Serial monitor

Dependencies

• ESP32 Arduino core
• ArduinoJson — JSON (v7)
• Wire (I2C, built-in) — TEA6320T communication

Related Repositories

Repo	Role
carputer	Qt5 head unit — sends TCP commands
esp32_sensor_module	Connects to this module's WiFi AP
esp32_cluster	TFT display — connects to this module's WiFi AP
esp32_keyfob	ESP-NOW remote — sends lock/start commands
esp32_mesh_module	V2V mesh — talks to this module via TCP