From 6183f0faee4a8a379c229ddd4263addce1b33fd9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20St=C3=A4ck?= <stack@spotify.com>
Date: Mon, 23 Dec 2019 00:41:15 +0100
Subject: [PATCH] Test tool for MPR121 modules.

---
 TestMPR121/TestMPR121.ino | 153 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)
 create mode 100644 TestMPR121/TestMPR121.ino

diff --git a/TestMPR121/TestMPR121.ino b/TestMPR121/TestMPR121.ino
new file mode 100644
index 0000000..3ce7ab3
--- /dev/null
+++ b/TestMPR121/TestMPR121.ino
@@ -0,0 +1,153 @@
+#include <Wire.h>
+#include <Adafruit_MPR121.h>
+
+/*
+    Tool to test an MPR121 unit. Wires each touch input to a teensy pin to simulate touch sensor signals.
+    Used to detect faulty MPR121 units before assembly.
+*/
+
+Adafruit_MPR121 touchSensor = Adafruit_MPR121(); // This is the 12-input touch sensor
+
+//LED output pins. Red is the onboard one, other two are just wired via resistors to +3.3V
+#define RED_LED 13
+#define GREEN_LED 20
+#define YELLOW_LED 21
+
+void setup(void) {
+    Serial.begin(115200);
+
+    //Set all "test ports" to high-impedance for now
+    for(int i=0; i<=11; i++) {
+        pinMode(i, INPUT);
+    }
+
+    pinMode(RED_LED, OUTPUT); led(RED_LED, true);
+    pinMode(GREEN_LED, OUTPUT); led(GREEN_LED, true);
+    pinMode(YELLOW_LED, OUTPUT); led(YELLOW_LED, true);
+
+    delay(100);
+    int serialwait = 100; //Max time to wait for serial port initialization
+    while(!Serial && serialwait)
+    {
+        delay(1);
+        --serialwait;
+    }
+
+    led(RED_LED, false);
+    led(GREEN_LED, false);
+    led(YELLOW_LED, false);
+
+    Serial.println("Running MPR121 test");
+
+    if (!touchSensor.begin(0x5A)) {
+        //Bail out if MPR121 cannot be initialized (chip broken or not present).
+        Serial.println("MPR121 initialization failed!");
+        failure();
+        return;
+    } else {
+        Serial.println("MPR121 init ok.");
+    }
+
+    //Attempt some kind of random seeding
+    srandom(analogRead(0) ^ millis());
+    delay(200);
+
+    run_all();
+}
+
+void led(uint8_t pin, bool state) {
+    //Onboard red LED is wired a bit differently
+    if(pin != RED_LED) {
+        digitalWrite(pin, state?LOW:HIGH);
+    } else {
+        digitalWrite(pin, state?HIGH:LOW);
+    }
+}
+
+void set_touch_pins(uint16_t value)
+{
+    for(int pin=0; pin<12; ++pin)
+    {
+        uint16_t touched = (value >> pin) & 0x0001; //Mask out bit value of pin
+        int teensyPin = 11-pin; //Row of teensy pins is 0-11 but mirrored vs MPR121
+
+        if(touched) {
+            pinMode(teensyPin, INPUT_PULLDOWN);
+        } else {
+            pinMode(teensyPin, INPUT_PULLUP);
+        }
+    }
+}
+
+bool run_test(const char* name, uint16_t value) {
+    Serial.print(name);
+    set_touch_pins(value);
+    led(YELLOW_LED, true);
+    delay(50);
+    led(YELLOW_LED, false);
+    delay(50);
+    uint16_t t = touchSensor.touched();
+    Serial.print(", expected: ");
+    Serial.print(value, HEX);
+    Serial.print(" got: ");
+    Serial.print(t, HEX);
+
+    if(value == t) {
+        Serial.println(" PASS");
+        return true;
+    } else {
+        Serial.println(" FAIL");
+        return false;
+    }
+}
+
+void failure() {
+    led(RED_LED, true);
+    led(GREEN_LED, false);
+    Serial.println("Test failed!");
+}
+
+void success() {
+    led(RED_LED, false);
+    led(GREEN_LED, true);
+    Serial.println("All tests succeeded!");
+}
+
+//Macro to bail out on any failure
+#define TEST(x) if(!x) { failure(); return; }
+
+void run_all(void) {
+
+    TEST(run_test("ALL_OFF", 0x000));
+    TEST(run_test("ALL_ON", 0xFFF));
+
+    //Pins one at a time
+    TEST(run_test("P0", 0x001 << 0));
+    TEST(run_test("P1", 0x001 << 1));
+    TEST(run_test("P2", 0x001 << 2));
+    TEST(run_test("P3", 0x001 << 3));
+    TEST(run_test("P4", 0x001 << 4));
+    TEST(run_test("P5", 0x001 << 5));
+    TEST(run_test("P6", 0x001 << 6));
+    TEST(run_test("P7", 0x001 << 7));
+    TEST(run_test("P8", 0x001 << 8));
+    TEST(run_test("P9", 0x001 << 9));
+    TEST(run_test("P10", 0x001 << 10));
+    TEST(run_test("P11", 0x001 << 11));
+
+    //Alternating pattern
+    TEST(run_test("ODD", 0x0555));
+    TEST(run_test("EVEN", 0x0AAA));
+
+    //A few random ones for good measure
+    for(int i=0; i<8; i++) {
+        TEST(run_test("RANDOM", random() % 0x1000));
+    }
+
+    success();
+}
+
+//Dummy loop does nothing
+void loop() {
+    delay(100);
+}
\ No newline at end of file