rpi4-osdev/part9-sound/kernel.c
2021-02-17 10:32:35 +00:00

110 lines
2.8 KiB
C

#include "fb.h"
#include "io.h"
#define PWM_BASE (PERIPHERAL_BASE + 0x20C000 + 0x800) /* PWM1 register base address on RPi4 */
#define CLOCK_BASE (PERIPHERAL_BASE + 0x101000)
#define BCM2711_PWMCLK_CNTL 40
#define BCM2711_PWMCLK_DIV 41
#define BCM2711_PWM_CONTROL 0
#define BCM2711_PWM_STATUS 1
#define BCM2711_PWM0_RANGE 4
#define BCM2711_PWM0_DATA 5
#define BCM2711_PWM_FIFO 6
#define BCM2711_PWM1_RANGE 8
#define BCM2711_PWM1_DATA 9
#define BCM2711_PWM1_USEFIFO 0x2000 /* Data from FIFO */
#define BCM2711_PWM1_ENABLE 0x0100 /* Channel enable */
#define BCM2711_PWM0_USEFIFO 0x0020 /* Data from FIFO */
#define BCM2711_PWM0_ENABLE 0x0001 /* Channel enable */
#define BCM2711_GAPO2 0x20
#define BCM2711_GAPO1 0x10
#define BCM2711_RERR1 0x8
#define BCM2711_WERR1 0x4
#define BCM2711_FULL1 0x1
#define PM_PASSWORD 0x5A000000
#define ERRORMASK (BCM2711_GAPO2 | BCM2711_GAPO1 | BCM2711_RERR1 | BCM2711_WERR1)
volatile unsigned* clk = (void*)CLOCK_BASE;
volatile unsigned* pwm = (void*)PWM_BASE;
static void audio_init(void)
{
gpio_useAsAlt0(40); // Ensure PWM1 is mapped to GPIO 40/41
gpio_useAsAlt0(41);
wait_msec(2);
*(clk + BCM2711_PWMCLK_CNTL) = PM_PASSWORD | (1 << 5); // Stop clock
int idiv = 2;
*(clk + BCM2711_PWMCLK_DIV) = PM_PASSWORD | (idiv<<12);
*(clk + BCM2711_PWMCLK_CNTL) = PM_PASSWORD | 16 | 1; // Enable + oscillator
wait_msec(2);
// Disable PWM
*(pwm + BCM2711_PWM_CONTROL) = 0;
wait_msec(2);
*(pwm+BCM2711_PWM0_RANGE) = 0x264; // 44.1khz, Stereo, 8-bit (54Mhz / 44100 / 2)
*(pwm+BCM2711_PWM1_RANGE) = 0x264;
*(pwm+BCM2711_PWM_CONTROL) =
BCM2711_PWM1_USEFIFO |
BCM2711_PWM1_ENABLE |
BCM2711_PWM0_USEFIFO |
BCM2711_PWM0_ENABLE | 1<<6;
wait_msec(2);
}
void playaudio_cpu()
{
int i=0;
long status;
extern unsigned char _binary_audio_bin_start[];
extern unsigned char _binary_audio_bin_size[];
unsigned int size = (long)&_binary_audio_bin_size;
unsigned char *data = &(_binary_audio_bin_start[0]);
while (i < size) {
status = *(pwm + BCM2711_PWM_STATUS);
if (!(status & BCM2711_FULL1)) {
*(pwm+BCM2711_PWM_FIFO) = *(data + i);
i++;
*(pwm+BCM2711_PWM_FIFO) = *(data + i);
i++;
}
if ((status & ERRORMASK)) {
debugstr("error: ");
debughex(status);
debugcrlf();
*(pwm+BCM2711_PWM_STATUS) = ERRORMASK;
}
}
}
void main()
{
fb_init();
debugstr("Initialising audio... ");
audio_init();
debugstr("done"); debugcrlf();
debugstr("Starting to play sample using CPU"); debugcrlf();
playaudio_cpu();
debugstr("CPU finished playing sample"); debugcrlf();
while (1);
}