In the end I followed a different route. I never understood the point of changing the destination address with another DMA channel. I simplified things, just went with a simple 2 channel round robin, set the sample rate to double what I wanted and then de-interleaved the results from the single results array. I may revisit that example at some point to try and understand what they were trying to do.
The only thing I still don't understand is why I had to double the sample rate, i.e. I want to sample 20kHz audio, so need a sample rate of 40kHz, but I had to set the ADC sample rate to 80kHz in round robin mode to get the expected results.
In the setup I have:
and in the loop I have
And then I unpack the results from samples.
The only thing I still don't understand is why I had to double the sample rate, i.e. I want to sample 20kHz audio, so need a sample rate of 40kHz, but I had to set the ADC sample rate to 80kHz in round robin mode to get the expected results.
In the setup I have:
Code:
// ADC adc_gpio_init(ADC_GPIO_L); adc_gpio_init(ADC_GPIO_R); adc_init(); uint chan_mask = get_chan_mask(adc_vals); adc_set_round_robin(chan_mask); adc_fifo_setup(true, true, 1, false, false); // Set ADC clock divisor uint clock_div = uint(PICO_CLK / SAMPLE_FREQ - ADC_ADJ); adc_set_clkdiv(clock_div); dma_chan = dma_claim_unused_channel(true); dma_conf = dma_channel_get_default_config(dma_chan); channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_16); channel_config_set_read_increment(&dma_conf, false); channel_config_set_write_increment(&dma_conf, true); channel_config_set_dreq(&dma_conf, DREQ_ADC);Code:
// ADC Capture adc_select_input(ADC_CHANNEL_L); dma_channel_configure( dma_chan, &dma_conf, samples, &adc_hw->fifo, NUM_CHANNELS * FFT_BINS, true ); adc_run(true); dma_channel_wait_for_finish_blocking(dma_chan); adc_run(false); adc_fifo_drain();Statistics: Posted by StarryPied — Mon Feb 12, 2024 10:00 am