i did this ages ago

sig gen now outputs correct hi-frq signal

firmware/BikeUSBv2_test_generator/BikeUSBv2_test_generator.ino

@@ -1,26 +1,53 @@
 void setup() {
   Serial.begin(115200);
   pinMode(7, OUTPUT);
+  pinMode(6, OUTPUT);
+
+
+  noInterrupts();
+  // Clear registers
+  TCCR2A = 0;
+  TCCR2B = 0;
+  TCNT2 = 0;
+
+  // 10000 Hz (16000000/((24+1)*64))
+  OCR2A = 24;
+  // CTC
+  TCCR2A |= (1 << WGM21);
+  // Prescaler 64
+  TCCR2B |= (1 << CS22);
+  // Output Compare Match A Interrupt Enable
+  TIMSK2 |= (1 << OCIE2A);
+  interrupts();
+}
+
+uint16_t divider = 9999;
+uint16_t counter = 0;
+bool state = 0;
+ISR(TIMER2_COMPA_vect) {
+  counter++;
+  if (counter > divider) {
+    digitalWrite(7, state);
+    digitalWrite(6, !state);
+    state ^= 1;
+    counter = 0;
+  }
 }
 
 union {
   uint16_t i;
   uint8_t b[sizeof(i)];
 } val;
 
-uint16_t t = 100;
-
 void loop() {
   val.i = analogRead(A0);
   Serial.write(val.b, sizeof(val.b));
 
-  digitalWrite(7, (millis() % t) > (t / 2));
-
   if (Serial.available()) {
     switch (Serial.read()) {
-      case 't':
+      case 'F':
         delay(100);
-        t = Serial.parseInt();
+        divider = Serial.parseInt();
         break;
       case 'i': analogReference(INTERNAL);
       case 'd': analogReference(DEFAULT);