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zyphlar
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/*
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* Pin Discovery Tool for Toy PCB Brain Transplant
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*
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* Upload this to the XIAO nRF52840, then connect one breakout pin
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* at a time to the PROBE_PIN. Open Serial Monitor at 115200 baud.
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*
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* The tool will tell you:
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* - Resting voltage (VCC, GND, floating, pulled up/down)
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* - Whether it responds to button presses
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* - Whether it looks like an analog resistor ladder
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* - Suggested function (power, button, output, NC)
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*
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* Workflow:
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* 1. Desolder original MCU, solder SOP-16 breakout adapter
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* 2. Install batteries in toy
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* 3. Connect XIAO GND to toy GND (battery negative)
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* 4. For each breakout pin, connect it to PROBE_PIN with a jumper
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* 5. Type the pin number in Serial Monitor and press Enter
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* 6. Follow prompts (press buttons when asked, etc.)
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* 7. Tool builds a pin map as you go
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*/
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#include <Arduino.h>
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#define PROBE_PIN A0 // Connect test jumper here
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#define NUM_MCU_PINS 16 // SOP-16
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// Storage for discovered pin map
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struct PinInfo {
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char label[20];
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float voltage;
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bool discovered;
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};
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PinInfo pinMap[NUM_MCU_PINS + 1]; // 1-indexed
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void setup() {
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Serial.begin(115200);
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while (!Serial) delay(10);
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memset(pinMap, 0, sizeof(pinMap));
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Serial.println("╔══════════════════════════════════════════╗");
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Serial.println("║ Toy PCB Pin Discovery Tool v1.0 ║");
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Serial.println("║ Connect XIAO GND to toy battery GND ║");
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Serial.println("║ Connect one SOP pin at a time to A0 ║");
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Serial.println("╚══════════════════════════════════════════╝");
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Serial.println();
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Serial.println("Commands:");
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Serial.println(" 1-16 = Probe that SOP pin number");
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Serial.println(" map = Show current pin map");
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Serial.println(" auto = Auto-detect VCC and GND pins");
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Serial.println(" btn = Button detection mode (tests all states)");
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Serial.println(" ladder = Resistor ladder detection");
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Serial.println();
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Serial.print("> ");
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}
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// Read voltage on probe pin (0-3.3V range)
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float readVoltage() {
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analogReadResolution(12); // nRF52840 supports 12-bit ADC
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delay(10); // settle
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// Average multiple readings
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uint32_t sum = 0;
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for (int i = 0; i < 16; i++) {
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sum += analogRead(PROBE_PIN);
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delayMicroseconds(500);
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}
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float raw = sum / 16.0;
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return (raw / 4095.0) * 3.3; // Convert to voltage
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}
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// Check if pin is actively being driven or floating
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String classifyVoltage(float v) {
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if (v < 0.1) return "GND (hard low)";
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if (v < 0.4) return "Weak pulldown or low output";
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if (v > 3.1) return "VCC (hard high)";
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if (v > 2.5) return "Weak pullup (~3V)";
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if (v > 1.4 && v < 1.9) return "Floating (~mid-rail)";
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return "Unknown voltage";
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}
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// Test if the pin changes state (button detection)
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void testButton(int sopPin) {
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Serial.println("\n--- Button Detection ---");
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Serial.println("Watch the voltage while pressing each toy button.");
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Serial.println("Monitoring for 10 seconds...");
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Serial.println();
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float baseline = readVoltage();
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Serial.print("Baseline: ");
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Serial.print(baseline, 3);
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Serial.println("V");
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float minV = baseline, maxV = baseline;
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unsigned long start = millis();
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int changes = 0;
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float lastV = baseline;
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while (millis() - start < 10000) {
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float v = readVoltage();
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if (v < minV) minV = v;
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if (v > maxV) maxV = v;
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// Detect transitions
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if (abs(v - lastV) > 0.3) {
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changes++;
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Serial.print(" Change detected! ");
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Serial.print(lastV, 2);
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Serial.print("V → ");
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Serial.print(v, 2);
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Serial.print("V at t=");
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Serial.print((millis() - start) / 1000.0, 1);
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Serial.println("s");
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}
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lastV = v;
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delay(20);
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}
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Serial.println();
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Serial.print("Range: ");
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Serial.print(minV, 3);
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Serial.print("V to ");
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Serial.print(maxV, 3);
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Serial.println("V");
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Serial.print("Transitions detected: ");
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Serial.println(changes);
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if (changes > 0 && maxV - minV > 1.0) {
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Serial.println("→ LIKELY A BUTTON PIN (digital, active low)");
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if (sopPin > 0) {
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snprintf(pinMap[sopPin].label, sizeof(pinMap[sopPin].label), "Button");
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pinMap[sopPin].voltage = baseline;
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pinMap[sopPin].discovered = true;
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}
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} else if (changes > 0 && maxV - minV > 0.2) {
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Serial.println("→ POSSIBLE ANALOG INPUT or RESISTOR LADDER");
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} else {
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Serial.println("→ No button activity detected on this pin");
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}
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}
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// Detect resistor ladder (multiple buttons on one analog pin)
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void testResistorLadder() {
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Serial.println("\n--- Resistor Ladder Detection ---");
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Serial.println("Press each button ONE AT A TIME when prompted.");
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Serial.println("Press Enter after pressing each button.");
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Serial.println("Type 'done' when finished.");
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Serial.println();
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float voltages[10];
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String names[10];
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int count = 0;
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float baseline = readVoltage();
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Serial.print("Baseline (no button): ");
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Serial.print(baseline, 3);
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Serial.println("V");
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while (count < 10) {
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Serial.print("\nPress button #");
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Serial.print(count + 1);
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Serial.println(" and type its name (or 'done'):");
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Serial.print("> ");
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while (!Serial.available()) delay(10);
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String input = Serial.readStringUntil('\n');
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input.trim();
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if (input.equalsIgnoreCase("done")) break;
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float v = readVoltage();
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voltages[count] = v;
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names[count] = input;
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Serial.print(" ");
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Serial.print(input);
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Serial.print(": ");
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Serial.print(v, 3);
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Serial.println("V");
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count++;
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Serial.println(" Release button now.");
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delay(500);
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}
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if (count > 1) {
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Serial.println("\n--- Ladder Summary ---");
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Serial.print("Baseline: ");
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Serial.print(baseline, 3);
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Serial.println("V");
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for (int i = 0; i < count; i++) {
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Serial.print(" ");
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Serial.print(names[i]);
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Serial.print(": ");
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Serial.print(voltages[i], 3);
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Serial.print("V (ADC ~");
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Serial.print((int)(voltages[i] / 3.3 * 4095));
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Serial.println(")");
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}
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// Check if voltages are distinct enough
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bool isLadder = true;
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for (int i = 0; i < count - 1; i++) {
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for (int j = i + 1; j < count; j++) {
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if (abs(voltages[i] - voltages[j]) < 0.15) {
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isLadder = false;
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}
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}
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}
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if (isLadder && count >= 2) {
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Serial.println("\n→ THIS IS A RESISTOR LADDER");
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Serial.println(" Use analogRead() with thresholds to detect buttons.");
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Serial.println(" Suggested thresholds (midpoints between readings):");
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// Sort by voltage
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for (int i = 0; i < count - 1; i++) {
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for (int j = i + 1; j < count; j++) {
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if (voltages[j] < voltages[i]) {
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float tv = voltages[i]; voltages[i] = voltages[j]; voltages[j] = tv;
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String ts = names[i]; names[i] = names[j]; names[j] = ts;
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}
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}
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}
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for (int i = 0; i < count; i++) {
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float lo = (i == 0) ? 0 : (voltages[i-1] + voltages[i]) / 2;
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float hi = (i == count-1) ? 3.3 : (voltages[i] + voltages[i+1]) / 2;
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Serial.print(" ");
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Serial.print(names[i]);
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Serial.print(": ");
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Serial.print(lo, 2);
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Serial.print("V - ");
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Serial.print(hi, 2);
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Serial.println("V");
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}
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} else {
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Serial.println("\n→ Doesn't look like a resistor ladder");
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Serial.println(" (Voltages too close together or too few buttons)");
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}
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}
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}
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// Full probe of one pin
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void probePin(int sopPin) {
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Serial.print("\n═══ Probing SOP-16 Pin ");
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Serial.print(sopPin);
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Serial.println(" ═══");
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// First read as analog input (high impedance)
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pinMode(PROBE_PIN, INPUT);
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delay(50);
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float v_floating = readVoltage();
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Serial.print("Floating voltage: ");
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Serial.print(v_floating, 3);
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Serial.print("V → ");
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Serial.println(classifyVoltage(v_floating));
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// Classify
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if (v_floating < 0.1) {
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Serial.println("→ This is a GND pin");
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snprintf(pinMap[sopPin].label, sizeof(pinMap[sopPin].label), "GND");
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pinMap[sopPin].voltage = v_floating;
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pinMap[sopPin].discovered = true;
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}
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else if (v_floating > 2.8) {
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// Could be VCC or a pulled-up button pin
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// Try briefly enabling internal pulldown to see if it drops
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pinMode(PROBE_PIN, INPUT_PULLDOWN);
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delay(50);
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float v_pulldown = readVoltage();
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pinMode(PROBE_PIN, INPUT);
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if (v_pulldown > 2.5) {
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Serial.print("With pulldown: ");
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Serial.print(v_pulldown, 3);
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Serial.println("V — Still high → VCC (power) pin");
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snprintf(pinMap[sopPin].label, sizeof(pinMap[sopPin].label), "VCC");
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pinMap[sopPin].voltage = v_floating;
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pinMap[sopPin].discovered = true;
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} else {
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Serial.print("With pulldown: ");
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Serial.print(v_pulldown, 3);
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Serial.println("V — Dropped → Weak pullup (likely button input)");
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Serial.println("→ Try pressing buttons to confirm. Running button test...");
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testButton(sopPin);
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}
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}
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else if (v_floating > 0.4 && v_floating < 2.5) {
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Serial.println("Mid-range voltage. Could be:");
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Serial.println(" - Floating (not connected)");
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Serial.println(" - Part of a resistor ladder");
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Serial.println(" - An analog output");
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Serial.println("→ Try pressing buttons to see if it changes...");
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testButton(sopPin);
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}
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else {
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Serial.println("Low but not GND. Could be pulled-down output.");
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testButton(sopPin);
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}
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Serial.println();
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}
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// Print the current pin map
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void showMap() {
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Serial.println("\n╔════════════════════════════════════╗");
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Serial.println("║ Current Pin Map ║");
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Serial.println("╠════════════════════════════════════╣");
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for (int i = 1; i <= NUM_MCU_PINS; i++) {
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Serial.print("║ Pin ");
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if (i < 10) Serial.print(" ");
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Serial.print(i);
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Serial.print(": ");
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if (pinMap[i].discovered) {
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Serial.print(pinMap[i].label);
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// Pad to align
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for (int j = strlen(pinMap[i].label); j < 12; j++) Serial.print(" ");
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Serial.print("(");
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Serial.print(pinMap[i].voltage, 2);
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Serial.print("V)");
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} else {
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Serial.print("-- not probed -- ");
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}
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Serial.println(" ║");
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}
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Serial.println("╚════════════════════════════════════╝");
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// Count discovered
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int found = 0;
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for (int i = 1; i <= NUM_MCU_PINS; i++) {
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if (pinMap[i].discovered) found++;
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}
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Serial.print("Discovered: ");
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Serial.print(found);
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Serial.print("/");
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Serial.println(NUM_MCU_PINS);
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}
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void loop() {
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if (Serial.available()) {
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String input = Serial.readStringUntil('\n');
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input.trim();
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if (input.equalsIgnoreCase("map")) {
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showMap();
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}
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else if (input.equalsIgnoreCase("btn")) {
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Serial.println("Connect the pin you want to test to A0, then:");
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testButton(0);
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}
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else if (input.equalsIgnoreCase("ladder")) {
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testResistorLadder();
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}
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else if (input.equalsIgnoreCase("auto")) {
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Serial.println("\n--- Auto-detect mode ---");
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Serial.println("Connect each pin to A0 one at a time.");
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Serial.println("Press Enter after connecting each pin.");
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for (int pin = 1; pin <= NUM_MCU_PINS; pin++) {
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Serial.print("\nConnect SOP pin ");
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Serial.print(pin);
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Serial.println(" to A0, then press Enter");
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Serial.print("> ");
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while (!Serial.available()) delay(10);
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Serial.readStringUntil('\n');
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probePin(pin);
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}
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showMap();
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}
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else {
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int pin = input.toInt();
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if (pin >= 1 && pin <= NUM_MCU_PINS) {
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probePin(pin);
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} else {
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Serial.println("Unknown command. Use 1-16, map, auto, btn, or ladder");
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}
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}
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Serial.print("\n> ");
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}
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}
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Reference in New Issue
Block a user