rfl

4ch RC receiver/transmitter with switched diversity antennas to retrofit 35MHz remotes.

• PPM input on CH3 to connect to old 35MHz internal PPM signal
• Dual U.fl connectors for antennas (single transmit, dual receive)
• 4 PWM outputs (3.3V)
• USB-C for programming

Parts

• SX1281 2.4GHz Transceiver IC
• SE2431L LNA/PA with up to +24 dBm
• STM32G0B1KET6N MCU
• TPS7A19 with up to 40V Vin

Assembly

QFN parts need a reflow oven/hot air station, the rest is 0402 or larger.

Fimware

First prototype implementation with fixed frequency hopping table, very simple Rx-antenna diversity is "useable". The firmware currently checks for a valid PPM input if thats not found switches to receiver mode.