Custom keyboard v2 - MCP23017 split breadboard, research QMK support

1 files changed, 75 insertions, 3 deletions

diff --git a/Custom keyboard V2/index.md b/Custom keyboard V2/index.md
index d01e060..90dc5a2 100755
--- a/Custom keyboard V2/index.md
+++ b/Custom keyboard V2/index.md
@@ -272,8 +272,8 @@ And i followed the wiring described therein. Namely, tie `A0`, `A1` and `A2` to
 ### MCP23017 C++ code snippet
 
 ```c++
-https://blog.node5.net/Custom%20keyboard%20V2#mcp23017-c-code-snippet
-Based on: https://github.com/adafruit/Adafruit-MCP23017-Arduino-Library/blob/master/examples/mcp23xxx_blink/mcp23xxx_blink.ino
+// https://blog.node5.net/Custom%20keyboard%20V2#mcp23017-c-code-snippet
+// Based on: https://github.com/adafruit/Adafruit-MCP23017-Arduino-Library/blob/master/examples/mcp23xxx_blink/mcp23xxx_blink.ino
 // Blinks an LED attached to a MCP23017 pin.
 
 #include <Adafruit_MCP23X17.h>
@@ -322,4 +322,76 @@ I've iterated on the thumb cluster design (based on the amazing work by the [Dyg
 and I've reached a design that works for me.
 
 ![Thumb cluster CAD based on Dygma Defy](Thumb cluster CAD based on Dygma Defy.png)
-![Thumb cluster itterations](Thumb cluster itterations.jpg)
\ No newline at end of file
+![Thumb cluster itterations](Thumb cluster itterations.jpg)
+
+### Other QMK keyboards using MCP23017
+
+MCP23017 working principle has been tested. Now it's time to make it work with QMK.
+The following keyboards implement the MCP23017. 
+
+```bash
+~/qmk $ grep --color=always -rnie "mcp23017" | cut -d'/' -f2 | uniq
+```
+- [nek_type_a](https://github.com/qmk/qmk_firmware/tree/master/keyboards/nek_type_a)
+- [hotdox](https://github.com/qmk/qmk_firmware/tree/master/keyboards/hotdox)
+- [ergodox_stm32](https://github.com/qmk/qmk_firmware/tree/master/keyboards/ergodox_stm32)
+- [ingrained](https://github.com/qmk/qmk_firmware/tree/master/keyboards/ingrained)
+- [ferris](https://github.com/qmk/qmk_firmware/tree/master/keyboards/ferris)
+
+### MCP23017 breadboard TRRS cable
+
+![MCP23017 breadboard TRRS cable](MCP23017 breadboard TRRS cable.jpg)
+
+I've now moved to using 2 separate breadboards to test if the I²C is stable over the cable (it seems to be).
+Pulling the TRRS cable while powered, doesn't break it, but does require a power cycle to function again.
+
+### MCP23017 button code
+
+```c++
+// https://blog.node5.net/Custom%20keyboard%20V2#mcp23017-button-code
+// Based on: https://github.com/adafruit/Adafruit-MCP23017-Arduino-Library/blob/master/examples/mcp23xxx_combo/mcp23xxx_combo.ino
+#include <Adafruit_MCP23X17.h>
+
+
+#define BLINK_FREQUENCY 1000 // Milliseconds
+#define LED_PIN         8    // LED pin on MCP23017
+#define BUTTON_PIN      7    // Button pin on MCP23017
+
+Adafruit_MCP23X17 mcp;
+int blink_frequency; // Milliseconds
+
+void setup() {
+	Serial.begin(9600);
+	//while (!Serial);
+	Serial.println("MCP23017 Blink Test!");
+	int i = 0;
+	while (!mcp.begin_I2C(i)) {
+  		Serial.print("Error with ID:");
+		Serial.println(i);
+    	i++;
+    	delay(10);
+	}
+	Serial.print("Success with ID:");
+	Serial.println(i);
+
+	mcp.pinMode(LED_PIN, OUTPUT);
+	mcp.pinMode(BUTTON_PIN, INPUT_PULLUP);
+	
+	Serial.println("Looping...");
+}
+
+void loop() {
+	// What is an interupt?
+	if (!mcp.digitalRead(BUTTON_PIN)) {
+		// Button pushed, light LED
+		blink_frequency = BLINK_FREQUENCY / 20;
+	} else {	
+		blink_frequency = BLINK_FREQUENCY; // Milliseconds
+	}
+		// Alternate state every blink_frequency milliseconds
+		bool state = (millis() % (blink_frequency * 2)) > blink_frequency;
+		Serial.print("State: ");
+		Serial.println(state);
+  	mcp.digitalWrite(LED_PIN, state);
+}
+```