FireWatchTower_2axis/firmware

Firmware

Arduino sketch for the LattePanda's onboard ATmega32U4 (Leonardo). Controls two stepper motor axes via TMC5160 drivers, manages thermal regulation, and communicates with the host over the serial link.

PlatformIO Configuration

Target: leonardo (ATmega32U4) at 115200 baud.

pio run --environment megaatmega2560 --target upload

Dependencies

Library	Version	Purpose
adafruit/DHT sensor library	^1.4.4	DHT22 temperature/humidity readings
adafruit/Adafruit Unified Sensor	^1.1.4	Unified sensor abstraction
TMC5160 (bundled)	—	Stepper motor driver via SPI

Architecture

src/
├── main.cpp              # Entry point, main loop
├── config/
│   ├── Constants.h       # All tunable parameters
│   └── Pins.h            # Pin assignments
├── motor/
│   ├── MotorConfig.h     # Axis IDs, status enum
│   ├── MotorDriver.*     # TMC5160 initialization, power control
│   ├── MotorAxis.*       # Per-axis state, register reads, SGT/encoder handling
│   └── Homing.*          # Endstop homing routine
├── serial/
│   └── CommandParser.*   # Serial command dispatch
└── thermal/
    └── ThermalManager.*  # DHT sensor + PWM fan control

Pinout

Pin	Function
0	TMC5160 ENABLE (Pitch)
1	TMC5160 CS (Pitch)
7	TMC5160 ENABLE (Yaw)
8	TMC5160 CS (Yaw)
9	DHT22 DATA
10	Fan PWM
11	Fan sense

Motor Configuration

Both axes use TMC5160 stepper drivers with closed-loop control.

Parameter	Yaw	Pitch
Steps/round	177,000	500,000
Gear ratio	739.556	739.556
Global scaler	80	50
Default Vmax	50,000	250,000
Endstop speed	25,000	150,000

Key constants in config/Constants.h:

• ENC_DEVIATION_LIMIT — Maximum allowed encoder-position deviation (1500 steps)
• ACCELERATION — Default acceleration profile (20,000)

Gimbal Status States

typedef enum {
    GIMBAL_STATUS_ERROR     = -2,
    GIMBAL_STATUS_BOOT      = -1,
    GIMBAL_STATUS_RESET      = 0,
    GIMBAL_STATUS_ENC_INIT   = 1,
    GIMBAL_STATUS_INITIALIZED= 2,
    GIMBAL_STATUS_AUTO       = 3,
    GIMBAL_STATUS_MANUAL     = 4
} gimbal_status;

Serial Protocol

Commands are received character-by-character. A leading command character is followed by optional comma-separated numeric arguments (hex by default; append d for decimal).

Command Reference

Command	Args	Description
r	—	Reset motor params, power on both axes
q	—	Run endstop homing on yaw then pitch
!	—	Power off both motors
*	—	Power on both motors
m	pos, speed	Move yaw to position with given speed
s	—	Stop both motors
b	—	Reset encoder deviation warning flags
t	—	Set Xenc to Xact (sync encoder to actual position)
e	—	Reset SGT (step goal threshold) on both axes
w	value	Set SGT value
u	step_len	Set auto-scan step length (must be > 2)
h	axis, hdg	Set heading calibration, save to EEPROM
y	axis	Load heading calibration from EEPROM
d	—	Set yaw to manual mode
p	—	Step yaw to next position (used for scan trigger)
v	speed	Set yaw Vmax
+	—	Record right encoder position
-	—	Record left encoder position
/	right, left	Set right and left encoder positions
?	—	Print encoder range info
;	value	Write raw value to Yaw register 0x21

Telemetry Output

Every INFO_PRINT_INTERVAL_MS (250 ms), both axes print status lines prefixed with $:

$Xenc;Xerr;sgt_val;sgt_stat;is_moving;control_status;hdg;deviation_warn;humid;temp;fan_pwm

Thermal Management

DHT22 sensor on pin 9 drives a PWM fan on pin 10.

Parameter	Value	Description
THERMAL_FAN_ON_TEMP	25°C	Fan activation threshold
THERMAL_FAN_GAIN	20	PWM gain per degree above threshold
THERMAL_FAN_MAX_PWM	255	Maximum PWM duty cycle
THERMAL_LOOP_INTERVAL	250 ms	Sensor read interval

Fan PWM = min(255, (temp - 25) * 20)

EEPROM Storage

Heading calibration data is stored at EEPROM address 0:

• Offset 0: float — current heading (c_hdg)
• Offset 4: int32_t — encoder distance offset from heading reference