"Sound"

[consp]

Sound info from the simple play command (have not looked into the gui file yeet):

The play command does the following:

• determines which pwm to use
• determines which "song" to play
• opens enable, duty_cycle and period and export
• loops over the data and calculates the duration/ds/period etc

Relevant loop code, setup is done, enable is triggered and when the note has played enable is set to 0.

          if ((iVar4 == 2) && (local_1c != 0)) {
            local_20 = 0;
            while ((*(int *)(local_20 * 8 + local_1c) != 0 ||
                   (*(int *)(local_20 * 8 + local_1c + 4) != 0))) {
              if (*(int *)(local_20 * 8 + local_1c) < 1) {
                usleep(*(int *)(local_20 * 8 + local_1c + 4) * 1000);
              }
              else {
                local_34 = __aeabi_idiv(1000000000,*(undefined4 *)(local_20 * 8 + local_1c));
                local_38 = local_34 / 2;
                sprintf(acStack_a8,"%d",local_34);
                local_3c = strlen(acStack_a8);
                write(file_3,acStack_a8,local_3c);
                sprintf(acStack_a8,"%d",local_38);
                local_3c = strlen(acStack_a8);
                write(file_4,acStack_a8,local_3c);
                write(file_enable,&ONE,1);
                usleep(*(int *)(local_20 * 8 + local_1c + 4) * 1000);
                write(file_enable,&ZERO,1);
              }
              local_20 = local_20 + 1;
            }
          }

This is 8086 speaker teritory.

The "file format" is an array[2] of int32 indicating the frequency and the duration. Pauses are indicated by setting the frequency to 0.

Pseudocode

index = 0
while(music[index][0] != 0 && music[index][1] != 0) {
    if (music[index][0] == 0) usleep(music[index][1] * 1000);
    else {
        period = (1000000000 / music[index][0]) / 2;
        duty_cycle = period/2;
        write(fp_period, period);
        write(fp_dc, duty_cucle);
        write(fp_enable, 1);
        usleep(music[index][1] * 1000);
        write(fp_enable, 0);
    }
}

Converted the doom song to frequency domain and tried playing it as a single frequency but no joy. If you slam the linux pwm driver it freezes after about 30-50 samples and stops functioning completely after a very short while. Don't spam it too much if you like the "tunes".

[consp]

Closed due to being in klipperscreen feature branch. (via buildroot packages)