DIY Interface Concept (Part 3/4) – Receive Port (RX)

Go here for Raspberry Pi 2/3 GPIO Pin Reference to connect your circuits described below.

Radio Port Interfaces – SQL (ACTIVE LOW TYPE)

From your receiver radio, locate the squelch detect output (commonly labeled COS/COR/SQL) signal and route this signal into the raspberry Pi GPIO (be sure to avoid the multi-function pins like I2s/I2c/SPI/etc). This diagram is for active low SQL signals which is the most common configuration. WARNING, YOUR RADIO SIGNALS CAN DAMAGE THE RPI IF YOU HOOK THIS UP INCORRECTLY!

Radio port interfaces – SQL (ACTIVE HIGH TYPE)

From your receiver radio, locate the squelch detect output (commonly labeled COS/COR/SQL) signal and route this signal into the raspberry Pi GPIO (be sure to avoid the multi-function pins like I2s/I2c/SPI/etc). This diagram is for active high SQL signals which is the less common configuration. Rbase will be selected based on the voltage output of this signal, 1k should be a good starting point WARNING, YOUR RADIO SIGNALS CAN DAMAGE THE RPI IF YOU HOOK THIS UP INCORRECTLY!
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