Skip to content

Instantly share code, notes, and snippets.

@samyk

samyk/sin134-pdb-dma-dac.c

Last active September 8, 2020 19:17
Show Gist options
  • Save samyk/6273cf9a45d63a50c38c8b50a39a8f52 to your computer and use it in GitHub Desktop.
Save samyk/6273cf9a45d63a50c38c8b50a39a8f52 to your computer and use it in GitHub Desktop.
Download ZIP

Revisions

  1. samyk revised this gist Jan 6, 2017. 1 changed file with 1 addition and 0 deletions.
    1 change: 1 addition & 0 deletions sin134-pdb-dma-dac.c
    View file
    Original file line number Diff line number Diff line change
    @@ -1,5 +1,6 @@
    // Generating a 134kHz sine wave using Teensy 3.6 with virtually
    // 0 cpu usage by filling the DAC up via DMA triggered by PDB
    // -samy kamkar

    #include <DMAChannel.h>
    #include "pdb.h"
  2. samyk created this gist Jan 6, 2017.
    43 changes: 43 additions & 0 deletions sin134-pdb-dma-dac.c
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,43 @@
    // Generating a 134kHz sine wave using Teensy 3.6 with virtually
    // 0 cpu usage by filling the DAC up via DMA triggered by PDB

    #include <DMAChannel.h>
    #include "pdb.h"

    DMAChannel dma(false);

    static volatile uint16_t sinetable[] = {
    2048,2277,2503,2724,2936,3137,3324,3495,3648,3781,3892,3980,4044,4082,4095,4082,4044,3980,3892,3781,3648,3495,3324,3137,2936,2724,2503,2277,2048,1818,1592,1371,1159,958,771,600,447,314,203,115,51,13,0,13,51,115,203,314,447,600,771,958,1159,1371,1592,1818
    };

    void setup()
    {
    dma.begin(true); // allocate the DMA channel first

    SIM_SCGC2 |= SIM_SCGC2_DAC0; // enable DAC clock
    DAC0_C0 = DAC_C0_DACEN | DAC_C0_DACRFS; // enable the DAC module, 3.3V reference

    // slowly ramp up to DC voltage, approx 1/4 second
    for (int16_t i=0; i<2048; i+=8)
    {
    *(volatile int16_t *)&(DAC0_DAT0L) = i;
    delay(1);
    }

    // set the programmable delay block to trigger DMA requests
    SIM_SCGC6 |= SIM_SCGC6_PDB; // enable PDB clock
    PDB0_IDLY = 0; // interrupt delay register
    PDB0_MOD = 0; //PDB_PERIOD; // modulus register, sets period

    PDB0_SC = PDB_CONFIG | PDB_SC_LDOK; // load registers from buffers
    PDB0_SC = PDB_CONFIG | PDB_SC_SWTRIG; // reset and restart
    PDB0_CH0C1 = 0x0101; // channel n control register?

    dma.sourceBuffer(sinetable, sizeof(sinetable));
    dma.destination(*(volatile uint16_t *)&(DAC0_DAT0L));
    dma.triggerAtHardwareEvent(DMAMUX_SOURCE_PDB);
    dma.enable();
    }

    void loop() {
    }