From ae94deaa166e05612a349853f5724953806361eb Mon Sep 17 00:00:00 2001
From: dakkar <dakkar@thenautilus.net>
Date: Sun, 16 Aug 2020 11:41:47 +0100
Subject: matrix scanning

---
 Makefile       | 12 ++++++++++
 lego-piano.ino | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 Makefile
 create mode 100644 lego-piano.ino

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..a7d095c
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,12 @@
+SKETCH = lego-piano.ino
+
+UPLOAD_PORT = /dev/ttyUSB0
+# this is the board with the OLED
+#BOARD = lolin32
+# this is the more compact board with TTGO written on it
+BOARD = featheresp32
+
+ESP_ROOT = $(HOME)/HW/arduino-esp32
+CHIP = esp32
+
+include $(HOME)/src/makeEspArduino/makeEspArduino.mk
diff --git a/lego-piano.ino b/lego-piano.ino
new file mode 100644
index 0000000..4923159
--- /dev/null
+++ b/lego-piano.ino
@@ -0,0 +1,69 @@
+/*
+  matrix-scan a set of LEDs
+
+  pins:
+
+  "rows"
+  12 & 13 go to a 220Ω resistor, then to 2 LEDs each (positive / long stem side)
+
+  "columns"
+  14 & 15 go to 2 LEDs each (negative / short stem side)
+
+  so that given one of 12|13 and one of 14|15, one LED is identified
+ */
+
+int currentLed = 0;
+
+void setup() {
+  Serial.begin(19200);
+  pinMode(12, OUTPUT);
+  pinMode(13, OUTPUT);
+  pinMode(14, OUTPUT);
+  pinMode(15, OUTPUT);
+  currentLed = 0;
+}
+
+void tristate(int pin) {
+  pinMode(pin,OUTPUT);
+  digitalWrite(pin,LOW);
+  pinMode(pin,INPUT);
+}
+
+void power(int pin) {
+  pinMode(pin,OUTPUT);
+  digitalWrite(pin,HIGH);
+}
+
+void ground(int pin) {
+  pinMode(pin,OUTPUT);
+  digitalWrite(pin,LOW);
+}
+
+void enableRowCol(int row, int col) {
+  Serial.print("enabling ");
+  Serial.print(row);
+  Serial.print(" ");
+  Serial.println(col);
+
+  if (row==0) {
+    power(12); ground(13);
+  }
+  else {
+    ground(12); power(13);
+  }
+
+  if (col==0) {
+    ground(14); tristate(15);
+  }
+  else {
+    tristate(14); ground(15);
+  }
+}
+
+void loop() {
+  Serial.print("current led ");
+  Serial.println(currentLed);
+  enableRowCol(currentLed/2,currentLed%2);
+  currentLed = (currentLed+1)%4;
+  delay(10);
+}
\ No newline at end of file
-- 
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