|
| 1 | +/* Author: Nathan Seidle |
| 2 | + Created: July 24, 2019 |
| 3 | + License: MIT. See SparkFun Arduino Apollo3 Project for more information |
| 4 | +
|
| 5 | + This example shows how to modify the various PDM interface settings. |
| 6 | +*/ |
| 7 | + |
| 8 | +//Global variables needed for this sketch |
| 9 | +#define pdmDataBufferSize 4096 //Default is array of 4096 * 32bit |
| 10 | +uint32_t pdmDataBuffer[pdmDataBufferSize]; |
| 11 | +float g_fPDMTimeDomain[pdmDataBufferSize * 2]; |
| 12 | +float g_fPDMFrequencyDomain[pdmDataBufferSize * 2]; |
| 13 | +float g_fPDMMagnitudes[pdmDataBufferSize * 2]; |
| 14 | +uint32_t sampleFreq; |
| 15 | + |
| 16 | +//Enable these defines for additional debug printing |
| 17 | +#define PRINT_PDM_DATA 0 |
| 18 | +#define PRINT_FFT_DATA 0 |
| 19 | + |
| 20 | +#include <PDM.h> //Include PDM library included with the Aruino_Apollo3 core |
| 21 | +AP3_PDM myPDM; //Create instance of PDM class |
| 22 | + |
| 23 | +//Math library needed for FFT |
| 24 | +#define ARM_MATH_CM4 |
| 25 | +#include <arm_math.h> |
| 26 | + |
| 27 | +void setup() |
| 28 | +{ |
| 29 | + Serial.begin(9600); |
| 30 | + Serial.println("SparkFun PDM Example"); |
| 31 | + |
| 32 | + // Turn on the PDM, set it up for our chosen recording settings, and start |
| 33 | + // the first DMA transaction. |
| 34 | + if (myPDM.begin(22, 23) == false) //Data, clock - These are the pin names from variant file, not pad names |
| 35 | + { |
| 36 | + Serial.println("PDM Init failed. Are you sure these pins are PDM capable?"); |
| 37 | + while (1); |
| 38 | + } |
| 39 | + Serial.println("PDM Initialized"); |
| 40 | + |
| 41 | + //For more settings see the |
| 42 | + myPDM.setClockSpeed(AM_HAL_PDM_CLK_3MHZ); |
| 43 | + myPDM.setClockDivider(AM_HAL_PDM_MCLKDIV_1); |
| 44 | + myPDM.setGain(AM_HAL_PDM_GAIN_P210DB); |
| 45 | + myPDM.setChannel(AM_HAL_PDM_CHANNEL_STEREO); |
| 46 | + |
| 47 | + printPDMConfig(); |
| 48 | + |
| 49 | + myPDM.getData(pdmDataBuffer, pdmDataBufferSize); //This clears the current PDM FIFO and starts DMA |
| 50 | +} |
| 51 | + |
| 52 | +void loop() |
| 53 | +{ |
| 54 | + am_hal_interrupt_master_disable(); |
| 55 | + |
| 56 | + if (myPDM.available()) |
| 57 | + { |
| 58 | + printLoudest(); |
| 59 | + |
| 60 | + while (PRINT_PDM_DATA || PRINT_FFT_DATA); |
| 61 | + |
| 62 | + // Start converting the next set of PCM samples. |
| 63 | + myPDM.getData(pdmDataBuffer, pdmDataBufferSize); |
| 64 | + } |
| 65 | + |
| 66 | + // Go to Deep Sleep until the PDM ISR or other ISR wakes us. |
| 67 | + am_hal_sysctrl_sleep(AM_HAL_SYSCTRL_SLEEP_DEEP); |
| 68 | + |
| 69 | + am_hal_interrupt_master_enable(); |
| 70 | +} |
| 71 | + |
| 72 | +//***************************************************************************** |
| 73 | +// |
| 74 | +// Analyze and print frequency data. |
| 75 | +// |
| 76 | +//***************************************************************************** |
| 77 | +void printLoudest(void) |
| 78 | +{ |
| 79 | + float fMaxValue; |
| 80 | + uint32_t ui32MaxIndex; |
| 81 | + int16_t *pi16PDMData = (int16_t *) pdmDataBuffer; |
| 82 | + uint32_t ui32LoudestFrequency; |
| 83 | + |
| 84 | + // |
| 85 | + // Convert the PDM samples to floats, and arrange them in the format |
| 86 | + // required by the FFT function. |
| 87 | + // |
| 88 | + for (uint32_t i = 0; i < pdmDataBufferSize; i++) |
| 89 | + { |
| 90 | + if (PRINT_PDM_DATA) |
| 91 | + { |
| 92 | + Serial.printf("%d\n", pi16PDMData[i]); |
| 93 | + } |
| 94 | + |
| 95 | + g_fPDMTimeDomain[2 * i] = pi16PDMData[i] / 1.0; |
| 96 | + g_fPDMTimeDomain[2 * i + 1] = 0.0; |
| 97 | + } |
| 98 | + |
| 99 | + if (PRINT_PDM_DATA) |
| 100 | + { |
| 101 | + Serial.printf("END\n"); |
| 102 | + } |
| 103 | + |
| 104 | + // |
| 105 | + // Perform the FFT. |
| 106 | + // |
| 107 | + arm_cfft_radix4_instance_f32 S; |
| 108 | + arm_cfft_radix4_init_f32(&S, pdmDataBufferSize, 0, 1); |
| 109 | + arm_cfft_radix4_f32(&S, g_fPDMTimeDomain); |
| 110 | + arm_cmplx_mag_f32(g_fPDMTimeDomain, g_fPDMMagnitudes, pdmDataBufferSize); |
| 111 | + |
| 112 | + if (PRINT_FFT_DATA) |
| 113 | + { |
| 114 | + for (uint32_t i = 0; i < pdmDataBufferSize / 2; i++) |
| 115 | + { |
| 116 | + Serial.printf("%f\n", g_fPDMMagnitudes[i]); |
| 117 | + } |
| 118 | + |
| 119 | + Serial.printf("END\n"); |
| 120 | + } |
| 121 | + |
| 122 | + // |
| 123 | + // Find the frequency bin with the largest magnitude. |
| 124 | + // |
| 125 | + arm_max_f32(g_fPDMMagnitudes, pdmDataBufferSize / 2, &fMaxValue, &ui32MaxIndex); |
| 126 | + |
| 127 | + ui32LoudestFrequency = (sampleFreq * ui32MaxIndex) / pdmDataBufferSize; |
| 128 | + |
| 129 | + if (PRINT_FFT_DATA) |
| 130 | + { |
| 131 | + Serial.printf("Loudest frequency bin: %d\n", ui32MaxIndex); |
| 132 | + } |
| 133 | + |
| 134 | + Serial.printf("Loudest frequency: %d \n", ui32LoudestFrequency); |
| 135 | +} |
| 136 | + |
| 137 | +//***************************************************************************** |
| 138 | +// |
| 139 | +// Print PDM configuration data. |
| 140 | +// |
| 141 | +//***************************************************************************** |
| 142 | +void printPDMConfig(void) |
| 143 | +{ |
| 144 | + uint32_t PDMClk; |
| 145 | + uint32_t MClkDiv; |
| 146 | + float frequencyUnits; |
| 147 | + |
| 148 | + // |
| 149 | + // Read the config structure to figure out what our internal clock is set |
| 150 | + // to. |
| 151 | + // |
| 152 | + switch (myPDM.getClockDivider()) |
| 153 | + { |
| 154 | + case AM_HAL_PDM_MCLKDIV_4: MClkDiv = 4; break; |
| 155 | + case AM_HAL_PDM_MCLKDIV_3: MClkDiv = 3; break; |
| 156 | + case AM_HAL_PDM_MCLKDIV_2: MClkDiv = 2; break; |
| 157 | + case AM_HAL_PDM_MCLKDIV_1: MClkDiv = 1; break; |
| 158 | + |
| 159 | + default: |
| 160 | + MClkDiv = 0; |
| 161 | + } |
| 162 | + |
| 163 | + switch (myPDM.getClockSpeed()) |
| 164 | + { |
| 165 | + case AM_HAL_PDM_CLK_12MHZ: PDMClk = 12000000; break; |
| 166 | + case AM_HAL_PDM_CLK_6MHZ: PDMClk = 6000000; break; |
| 167 | + case AM_HAL_PDM_CLK_3MHZ: PDMClk = 3000000; break; |
| 168 | + case AM_HAL_PDM_CLK_1_5MHZ: PDMClk = 1500000; break; |
| 169 | + case AM_HAL_PDM_CLK_750KHZ: PDMClk = 750000; break; |
| 170 | + case AM_HAL_PDM_CLK_375KHZ: PDMClk = 375000; break; |
| 171 | + case AM_HAL_PDM_CLK_187KHZ: PDMClk = 187000; break; |
| 172 | + |
| 173 | + default: |
| 174 | + PDMClk = 0; |
| 175 | + } |
| 176 | + |
| 177 | + // |
| 178 | + // Record the effective sample frequency. We'll need it later to print the |
| 179 | + // loudest frequency from the sample. |
| 180 | + // |
| 181 | + sampleFreq = (PDMClk / (MClkDiv * 2 * myPDM.getDecimationRate())); |
| 182 | + |
| 183 | + frequencyUnits = (float) sampleFreq / (float) pdmDataBufferSize; |
| 184 | + |
| 185 | + Serial.printf("Settings:\n"); |
| 186 | + Serial.printf("PDM Clock (Hz): %12d\n", PDMClk); |
| 187 | + Serial.printf("Decimation Rate: %12d\n", myPDM.getDecimationRate()); |
| 188 | + Serial.printf("Effective Sample Freq.: %12d\n", sampleFreq); |
| 189 | + Serial.printf("FFT Length: %12d\n\n", pdmDataBufferSize); |
| 190 | + Serial.printf("FFT Resolution: %15.3f Hz\n", frequencyUnits); |
| 191 | +} |
0 commit comments