feat(adc): ADC peripheral #13

Author: urish

src/index.ts

@@ -7,6 +7,16 @@
 export { CPU, ICPU, CPUMemoryHook, CPUMemoryHooks } from './cpu/cpu';
 export { avrInstruction } from './cpu/instruction';
 export { avrInterrupt } from './cpu/interrupt';
+export {
+  ADCConfig,
+  adcConfig,
+  ADCMuxConfiguration,
+  ADCMuxInput,
+  ADCMuxInputType,
+  ADCReference,
+  atmega328Channels,
+  AVRADC,
+} from './peripherals/adc';
 export {
   AVRTimer,
   AVRTimerConfig,

src/peripherals/adc.spec.ts

@@ -0,0 +1,137 @@
+import { CPU } from '../cpu/cpu';
+import { asmProgram, TestProgramRunner } from '../utils/test-utils';
+import { AVRADC, adcConfig, ADCMuxInputType } from './adc';
+
+const R16 = 16;
+const R17 = 17;
+
+const ADMUX = 0x7c;
+const REFS0 = 1 << 6;
+
+const ADCSRA = 0x7a;
+const ADEN = 1 << 7;
+const ADSC = 1 << 6;
+const ADPS0 = 1 << 0;
+const ADPS1 = 1 << 1;
+const ADPS2 = 1 << 2;
+
+const ADCH = 0x79;
+const ADCL = 0x78;
+
+describe('ADC', () => {
+  it('should successfuly perform an ADC conversion', () => {
+    const { program } = asmProgram(`
+    ; register addresses
+    _REPLACE ADMUX, ${ADMUX}
+    _REPLACE ADCSRA, ${ADCSRA}
+    _REPLACE ADCH, ${ADCH}
+    _REPLACE ADCL, ${ADCL}
+
+    ; Configure mux - channel 0, reference: AVCC with external capacitor at AREF pin
+    ldi r24, ${REFS0}
+    sts ADMUX, r24
+
+    ; Start conversion with 128 prescaler
+    ldi r24, ${ADEN | ADSC | ADPS0 | ADPS1 | ADPS2}
+    sts ADCSRA, r24
+
+    ; Wait until conversion is complete
+  waitComplete:
+    lds r24, ${ADCSRA}
+    andi r24, ${ADSC}
+    brne waitComplete
+
+    ; Read the result
+    lds r16, ${ADCL}
+    lds r17, ${ADCH}
+
+    break
+  `);
+    const cpu = new CPU(program);
+    const adc = new AVRADC(cpu, adcConfig);
+    const runner = new TestProgramRunner(cpu);
+
+    const adcReadSpy = jest.spyOn(adc, 'onADCRead');
+    adc.channelValues[0] = 2.56; // should result in 2.56/5*1024 = 524
+
+    // Setup
+    runner.runInstructions(4);
+    expect(adcReadSpy).toHaveBeenCalledWith({ channel: 0, type: ADCMuxInputType.SingleEnded });
+
+    // Run the "waitComplete" loop for a few cycles
+    runner.runInstructions(12);
+
+    cpu.cycles += 128 * 25; // skip to the end of the conversion
+    cpu.tick();
+
+    // Now read the result
+    runner.runInstructions(5);
+
+    const low = cpu.data[R16];
+    const high = cpu.data[R17];
+    expect((high << 8) | low).toEqual(524); // 2.56 volts - see above
+  });
+
+  it('should read 0 when the ADC peripheral is not enabled', () => {
+    // This behavior was verified on real hardware, using the following test program:
+    // https://wokwi.com/arduino/projects/309156042450666050
+    // Thanks Oscar Oomens for spotting this!
+
+    const { program } = asmProgram(`
+    ; register addresses
+    _REPLACE ADMUX, ${ADMUX}
+    _REPLACE ADCSRA, ${ADCSRA}
+    _REPLACE ADCH, ${ADCH}
+    _REPLACE ADCL, ${ADCL}
+
+    ; Load some initial value into r16/r17 to make sure we actually read 0 later
+    ldi r16, 0xff
+    ldi r17, 0xff
+
+    ; Configure mux - channel 0, reference: AVCC with external capacitor at AREF pin
+    ldi r24, ${REFS0}
+    sts ADMUX, r24
+
+    ; Start conversion with 128 prescaler, but without enabling the ADC
+    ldi r24, ${ADSC | ADPS0 | ADPS1 | ADPS2}
+    sts ADCSRA, r24
+
+    ; Wait until conversion is complete
+  waitComplete:
+    lds r24, ${ADCSRA}
+    andi r24, ${ADSC}
+    brne waitComplete
+
+    ; Read the result
+    lds r16, ${ADCL}
+    lds r17, ${ADCH}
+
+    break
+  `);
+    const cpu = new CPU(program);
+    const adc = new AVRADC(cpu, adcConfig);
+    const runner = new TestProgramRunner(cpu, () => {
+      /* do nothing on break */
+    });
+
+    const adcReadSpy = jest.spyOn(adc, 'onADCRead');
+    adc.channelValues[0] = 2.56; // should result in 2.56/5*1024 = 524
+
+    // Setup
+    runner.runInstructions(6);
+    expect(adcReadSpy).not.toHaveBeenCalled();
+
+    // Run the "waitComplete" loop for a few cycles
+    runner.runInstructions(12);
+
+    cpu.cycles += 128 * 25; // skip to the end of the conversion
+    cpu.tick();
+
+    // Now read the result
+    runner.runToBreak();
+
+    const low = cpu.data[R16];
+    const high = cpu.data[R17];
+    expect((high << 8) | low).toEqual(0); // We should read 0 since the ADC hasn't been enabled
+  });
+});