48 lines
1.4 KiB
Arduino
48 lines
1.4 KiB
Arduino
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// AtTiny412
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// 16Mhz tuned following https://github.com/SpenceKonde/megaTinyCore/blob/master/megaavr/extras/Ref_Tuning.md
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// millis/micros disabled
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#include <Arduino.h>
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constexpr uint8_t LUT_SIZE = 24;
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constexpr uint8_t LUT_SIZE_HALF = LUT_SIZE*0.5;
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constexpr uint8_t LUT_SIZE_QUARTER = LUT_SIZE*0.25;
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constexpr uint8_t MAX_VALUE = 64;
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constexpr float SAMPLE_FREQ = 57500.0;
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uint8_t SINE_LUT[LUT_SIZE];
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//constexpr float delta_phi = 4000.0f / SAMPLE_FREQ * (float)LUT_SIZE;
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constexpr float delta_phi = 0.07052234f * (float)LUT_SIZE;
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float phase = 0;
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// constexpr uint8_t ddelta_phi = 0.05465 * LUT_SIZE;
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// uint8_t phase = 0;
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void setup() {
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DACReference(INTERNAL4V3);
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for (uint8_t i = 0; i < LUT_SIZE; i++) {
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// SINE_LUT[i] = (0.5f + 0.5*sin((2 * PI * (float)i) / LUT_SIZE)) * MAX_VALUE;
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//For the first quarter of the lut, generate a quarter of a sine wave
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if(i >= 0 && i <= LUT_SIZE_QUARTER) SINE_LUT[i] = (0.5f + 0.5*sin((2 * PI * (float)i) / LUT_SIZE)) * MAX_VALUE; // (uint8_t) (MAX_VALUE_HALF + (MAX_VALUE_HALF-1) * sin((2 * PI * (float)i) / LUT_SIZE));
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else if(i > LUT_SIZE_QUARTER && i <= LUT_SIZE_HALF) SINE_LUT[i] = SINE_LUT[(LUT_SIZE_HALF-i)];
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else SINE_LUT[i] = MAX_VALUE-SINE_LUT[(LUT_SIZE-i)];
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}
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DAC0.CTRLA |= 0x41;
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while(1){
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phase += delta_phi;
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// handle wraparound
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if (phase >= LUT_SIZE) phase -= LUT_SIZE;
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DAC0.DATA = SINE_LUT[(uint8_t)phase];
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}
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}
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void loop() {
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}
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