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README.md

Meteomodem M20

Description

Assembled Radiosonde

Exploded View

MCU and GPS

Radio

The Analog Devices ADF7012 FSK transmitter gets its reference clock from the 8 MHz MCO output of the MCU. The MCU handles the control interface of the radio via bit-banging over standard port pins. TX data is sent asynchronously to the ADF7012 TXDATA pin. The MCU generates transmit data with the help of TIMER21 and its TIM21_CH1 output. A PA (unknown type) boosts the output signal.

Modulation is 2FSK with 5.5 kHz deviation. Data bits are sent Biphase-M encoded in short bursts with 4800 bit/s (9600 smbols/s).

Analog

Powersupply

Theory of Operations

Main PCB Scan

Sensor Boom Scan

Still some stuff missing here...

Parts List

Designator	Function	Manufacturer	Part Number
U1	MCU	STM	STM32L051R6T6
U2	GPS Receiver	Sierra	XM1110
U3	Pressure Sensor (optional)	STM	LPS22HB
U101	Switching Regulator	Microchip	MCP1642B-ADJI/MS
U102-104	LDO	TI	LP5907MFX-3.3
U201	Transmitter	Analog Devices	ADF7012
U301	RC Oscillator	X	TL555I