[Keyboard] Enable Proton C defaults for SplitKB Kyria (#14490)

Co-authored-by: Ryan <fauxpark@gmail.com>

1 files changed, 21 insertions, 1 deletions

diff --git a/keyboards/splitkb/kyria/readme.md b/keyboards/splitkb/kyria/readme.md
index 5ce652589c..7ecf3946f7 100644
--- a/keyboards/splitkb/kyria/readme.md
+++ b/keyboards/splitkb/kyria/readme.md
@@ -10,7 +10,8 @@ Hardware Availability: [splitkb.com](https://splitkb.com) and partners.
 
 Make example for this keyboard (after setting up your build environment):
 
-    make splitkb/kyria:default
+    make splitkb/kyria/rev1:default
+    make splitkb/kyria/rev1/proton_c:default
 
 Example of flashing this keyboard:
 
@@ -19,3 +20,22 @@ Example of flashing this keyboard:
 See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).
 
 A build guide for the Kyria can be found at [docs.splitkb.com](https://docs.splitkb.com/hc/en-us/articles/360010552059-Kyria-Build-Guide-Introduction).
+
+## Proton C Conversion Guide
+
+If you're one of the lucky people to have Proton Cs to use with their Kyria, there are a couple of caveats to getting this working.
+
+1. You need to have 2x Proton Cs, as you cannot mix and match with Pro Micros or Elite C's.  They both need to be Proton Cs.
+2. You'll need to do some modding to enable proper support with the Proton C.
+
+By design, the Kyria uses every available pin on the Pro Micro footprint.  This includes using D3 (RX) for RGB.  This poses a challenge with using the Proton C, since it needs both the TX and RX pins. The Proton C needs both pins, especially if you plan on using Full Duplex Serial. 
+
+To fix this, you need to break off the last header position on the right-hand side on the footprint. This is the `TX0/D3` pad. Leave this pad without a header connected to.
+
+From the A9 pin on the Proton C, you want to run a wire from it to the `SDA + Extra Data` pad near the TRRS jack on the PCB. This will allow for proper, full duplex communication over the TRRS cable. 
+
+To get RGB working properly, as well, you want to run a wire from the `A3` pin on the Proton C, next to the GND and DFU pin, right under the USB port.  Run this to the `TX0/D3` pad (the one you left without a header pin on the PCB).
+
+Once you've done that, you can solder in the Proton C. and flash it.
+
+![Proton C](https://i.imgur.com/nICqWLo.jpg)