Ground Station

Pico 2W-based ground station for rocket tracking. Receives telemetry via dual LoRa radios, gets ground-station GPS position from Starlink over WiFi/MQTT, and drives two differential servo axes for antenna pointing.

Hardware Overview

Subsystem	Interface	Notes
LoRa 1 (SX1276)	SPI0	915 MHz telemetry RX
LoRa 2 (RFM69HCW)	SPI1	433 MHz backup / command link
GPS (ground station)	WiFi	Position from Starlink router via MQTT
Servo 1 (Zenith)	UART0 pins	Differential step/dir driver
Servo 2 (Azimuth)	UART1 pins	Differential step/dir driver
Barometer	I2C0	Not populated – future expansion
IMU + Magnetometer	I2C1	Not populated – future expansion

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Pico 2W Pinout

Phys Pin	GPIO	Signal	Notes
1	0	Servo 1 PUL+	UART0 TX repurposed as GPIO
2	1	Servo 1 PUL−	UART0 RX repurposed as GPIO
4	2	Servo 1 DIR+	UART0 CTS repurposed as GPIO
5	3	Servo 1 DIR−	UART0 RTS repurposed as GPIO
6	4	Servo 2 PUL+	UART1 TX repurposed as GPIO
7	5	Servo 2 PUL−	UART1 RX repurposed as GPIO
9	6	Servo 2 DIR+	UART1 CTS repurposed as GPIO
10	7	Servo 2 DIR−	UART1 RTS repurposed as GPIO
11	8	LoRa1 RST	SX1276 / 915 MHz
12	9	LoRa1 G0 (DIO0 / IRQ)	SX1276 / 915 MHz
14	10	LoRa1 EN	SX1276 / 915 MHz power enable
15	11	LoRa2 RST	RFM69HCW / 433 MHz
16	12	SPI1 MISO — LoRa2	RFM69HCW / 433 MHz
17	13	SPI1 CS — LoRa2	RFM69HCW / 433 MHz
19	14	SPI1 SCK — LoRa2	RFM69HCW / 433 MHz
20	15	SPI1 MOSI — LoRa2	RFM69HCW / 433 MHz
21	16	I2C0 SDA	Not populated (Barometer)
22	17	I2C0 SCL	Not populated (Barometer)
24	18	SPI0 SCK — LoRa1	SX1276 / 915 MHz
25	19	SPI0 MOSI — LoRa1	SX1276 / 915 MHz
26	20	SPI0 MISO — LoRa1	SX1276 / 915 MHz
27	21	SPI0 CS — LoRa1	SX1276 / 915 MHz
29	22	LoRa2 G0 (DIO0 / IRQ)	RFM69HCW / 433 MHz
31	26	I2C1 SDA	Not populated (IMU / Mag)
32	27	I2C1 SCL	Not populated (IMU / Mag)
34	28	LoRa2 EN	RFM69HCW / 433 MHz power enable

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Servo Connector Pinout

Each servo driver expects differential step/direction signals (e.g. RS-422 / open-collector driver).

Signal	Servo 1 (Zenith) GPIO	Servo 2 (Azimuth) GPIO	JST Pin
PUL+	0	4	1
PUL−	1	5	2
DIR+	2	6	3
DIR−	3	7	4

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LoRa Module Connector Pinout

Both LoRa headers share the same signal ordering. SPI bus differs per module.

Signal	LoRa1 (SX1276 / 915 MHz)	LoRa2 (RFM69HCW / 433 MHz)	JST Pin
EN	GPIO 10	GPIO 28	1
G0	GPIO 9	GPIO 22	2
SCK	GPIO 18 (SPI0)	GPIO 14 (SPI1)	3
MISO	GPIO 20 (SPI0)	GPIO 12 (SPI1)	4
MOSI	GPIO 19 (SPI0)	GPIO 15 (SPI1)	5
CS	GPIO 21 (SPI0)	GPIO 13 (SPI1)	6
RST	GPIO 8	GPIO 11	7
GND	—	—	8
3V3	—	—	9

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I2C Headers (not populated)

Bus	SDA	SCL	Planned Devices
I2C0	GPIO 16	GPIO 17	Barometer
I2C1	GPIO 26	GPIO 27	IMU, Magnetometer

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GPS

Ground-station position is obtained from a Starlink router over WiFi. No dedicated UART/GPIO pins are used. The Pico 2W connects to the router SSID and subscribes to a GPS MQTT topic (gs/gps).