Some good news for those who are looking for a cheap micro brushed FC, and only want to run Frsky TX. I managed to connect a PPM receiver to the Micro Scisky board (aka Quanum Pico).
The Scisky flight controller is an affordable board for micro brushed quadcopters. It allows you to run Cleanflight and Betaflight on it. Unfortunately it only comes with an integrated Spektrum DSM2 receiver, and there seemed to be no way of connecting a Frsky PPM receiver.
Many people including myself runs a Taranis, or other transmitters with Frsky TX module. Therefore we were unable to use this built-in RX without paying extra for an additional Orange TX module.
Fear no more! :) Here is how you can “hack” into the Scisky board, and enable PPM!
Find the PPM Receiver Pin
We can attach an external PPM receiver to the flight controller.
The PPM (CH1) pin’s location is shown below in the picture, and it’s covered in insulation material. You need to scrape off the solder mask to reveal the pin.
Use whatever tool you think sensible. I used a small pointy-ended file for the job. Be really careful and gentle, only work on the pin, and do not touch the traces/pins around it. Otherwise it would make soldering a lot harder and messier later on.
After you have scraped off the mask, apply some solder paste on the pin, and put a bit of solder on the pin with your soldering iron.
Connecting your favourite PPM Receiver
Depends on your choice of PPM receiver, choose whichever power suitable for it (5V or 3.3V).
I am using the SRP8 8CH PPM receiver, which requires 5V. If you use one of the Micro Frsky RX, then you might need 3.3V for it.
Here is a close up of the wire soldering (PPM, 5V and GND). Make sure you check the voltages with multimeter before connecting your receiver!
After that, Change Receiver Type to PPM in Cleanflight (originally Serial receiver), and you should now see the bars move with your sticks in the receiver tab :)
Lastly I think it would be a good idea to secure the wires/solder joints with hot glue. Especially the PPM pin is pretty weak.
Let me know if you have any comment, or know any other tricks with using the Pico FC.