kopia lustrzana https://github.com/mobilinkd/NucleoTNC
Use an 8-symbol length FIR filter for symbol interpolation.
rodzic
59783338c8
commit
4ac0001549
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@ -26,7 +26,9 @@ struct M17Modulator : Modulator
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// Six buffers per M17 frame, or 12 half-buffer interrupts.
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static constexpr uint8_t UPSAMPLE = 10;
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static constexpr uint32_t BLOCKSIZE = 4;
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static constexpr uint32_t STATE_SIZE = (m17::FILTER_TAP_NUM_15 / UPSAMPLE) + BLOCKSIZE - 1;
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static constexpr uint32_t STATE_SIZE = (m17::FILTER_TAP_NUM / UPSAMPLE) + BLOCKSIZE - 1;
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// Number of bytes (4 symbol groups) to flush the FIR filter.
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static constexpr uint8_t FLUSH_LEN = ((m17::FILTER_TAP_NUM / UPSAMPLE) + 3) / 4;
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static constexpr int16_t DAC_BUFFER_LEN = 80; // 8 symbols, 16 bits, 2 bytes.
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static constexpr int16_t TRANSFER_LEN = DAC_BUFFER_LEN / 2; // 4 symbols, 8 bits, 1 byte.
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static constexpr uint16_t VREF = 4095;
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@ -49,8 +51,8 @@ struct M17Modulator : Modulator
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: dacOutputQueueHandle_(queue), ptt_(ptt)
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{
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arm_fir_interpolate_init_f32(
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&fir_interpolator, UPSAMPLE, m17::FILTER_TAP_NUM_15,
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(float32_t*) m17::rrc_taps_f15.data(), fir_state.data(), BLOCKSIZE);
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&fir_interpolator, UPSAMPLE, m17::FILTER_TAP_NUM,
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(float32_t*) m17::rrc_taps_f.data(), fir_state.data(), BLOCKSIZE);
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}
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~M17Modulator() override {}
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@ -118,7 +120,7 @@ struct M17Modulator : Modulator
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start_conversion();
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ptt_->on();
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while (delay_count < txdelay) osThreadYield();
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stop_count = 4; // 16 symbols to flush the RRC filter.
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stop_count = FLUSH_LEN;
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osMessagePut(dacOutputQueueHandle_, bits, osWaitForever);
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state = State::RUNNING;
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break;
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