Step 1: Read through Rob Hart's tutorial for transmitting data between microcontrollers via nRF24L01 radios.

Step 2: Draw a schematic for your radio board following the steps outlined in the KiCad demo video but using the fab library components listed below and the layout shown in the photos. I used the following components from the fab library:

• ATTTINY44-SSU
• AVRISPSMD: 2x3 pin header
• FTDI-SMD-HEADER: 6 pin header
• NRF24L01+: radio, use footprint fab:fab-2X04_THRU
• REGULATORSOT23: 3.3V regulator
• RES-US1206FAB: 10k
• CAP-US1206FAB: 0.1uF, 1uF, 10uF

Pro tips: For some reason, the assigned footprint for the nRF24L01 (fab-2x04_THRU) didn't appear when I loaded the netlist from the schematic to the PCB. If you have this same problem, edit the footprint library using the following steps:

• Open KiCad's project manager and then click on the PCB footprint editor button.
• Navigate to the fab -> fab-2X04_THRU footprint. Double click on this footprint to open it up in the editor. No footprint will appear.
• Try double clicking on the next footprint, fab-2X05SMD. This time, you should see the footprint in the editor.
• Right click on fab-2X05SMD > Save As... and save a copy as fab-2X04_THRU. Feel free to write over the existing file; it's not helping us anyway.
• Now when you double click on the fab-2X04_THRU footprint, you should see the same footprint as the fab-2X05SMD.
• Right click on fab-2X04_THRU > Edit Footprint.
• Delete pads 9 and 10, and rearrange the pads to match the pad order photo.

As always, make sure you leave 2-3mm between your outer traces and the edge of the and 5-6mm between the FTDI footprints and the edge of the board so that the black part rests on the board, reducing mechanical load on your soldered joints. I also increased the track width from 0.25mm (too thin) to maybe 0.4mm. I've also found it useful to shift some of the not-to-be-exported PCB text so that it spills beyond the edge cut so that no edge cuts accidentally disappear in mods. Finally, don't forget to perform a design rules check to make sure everything's connected. Even then, I missed a trace between the 1uF capacitor and power, so I had to go back and solder a jumper wire on both boards.

Step 3: Export your traces and edge cuts for milling! I added "Radio 1" and "Radio 2" text and exported traces for each. This was helpful for me to differentiate between my transmitting and receiving boards.

Step 1: Import your traces and edge cuts, invert, and mill.

Step 2: Solder the components to your board.

Step 1: Save Rob's c code and makefile.

Step 2: Connect the transmitting board to your programmer AND to power.

Step 3: Open a terminal in the folder with the saved files and run "make -f tiny44_tx.make ProgrammerName." The relevant programmer name can be found in the makefile. Repeat process for the receiving board.

Pro tips: Electronics are like small animals that desperately want your attention. I finally finished my FabFTDI this week after having built the wrong one last week. I ran into a million and a half problems programming, but once I pretended not to care and started doing something else, the problem would magically resolve itself. I'm not a fan of this method of working, but I'm glad things started working in the end.

Step 4: Download and run CoolTerm. Connect both radios to your computer, and open one terminal for your transmitter and one terminal for your receiver. Connect, and watch the magic!