Add pwm example

src/examples/gpio_test/gpio_test.c

@@ -13,7 +13,7 @@
 
 int main(int argc, char **args)
 {
-    if (rpi_init() ==-1) {
+    if (rpi_init() == -1) {
         printf("initialization failed");
         return -1;
     }

src/examples/pwm_test/pwm_test.c

@@ -9,19 +9,46 @@
 
 int main(int argc, char **args)
 {
-    if(rpi_init() ==-1){
-	printf("initialization failed");
-	return -1;
+    if(rpi_init() == -1){
+        printf("initialization failed");
+        return -1;
     }
-   //configure GPIO pin
-    print_version();
+
+    // PIN_33: PWM0 [ALT0];
+    // PIN_32: PWM1 [ALT0];
+    // PIN_12: PWM0 [ALT5];
+    // PIN_35: PWM1 [ALT5];
+    // Configure GPIO pin as ALT5, so it could be used for PWM function
     rpi_gpio_fsel(PIN_12, RPI_GPIO_FSEL_ALT5);
-
-    pwm_init(RPI_PWM_CHANNEL_0, 1, 1);
-    pwm_set_clock(RPI_PWM_CLOCK_DIVIDER_16); //600khz
-    pwm_set_range(0, 1024);
-    pwm_set_data(0, 512);
+
+
+    // Initialize PWM Channel 0; Return 0 on success
+    if(pwm_init(RPI_PWM_CHANNEL_0, 1, 1)) {
+        printf("Initializing PWM fails \n");
+        exit(-1);
+    }
+
+    // RPI_PWM_CLOCK_DIVIDER_2048 = 2048, //9.375khz
+    // RPI_PWM_CLOCK_DIVIDER_1024 = 1024, //18.75khz
+    // RPI_PWM_CLOCK_DIVIDER_512  = 512,  //37.5khz
+    // RPI_PWM_CLOCK_DIVIDER_256  = 256,  //75khz
+    // RPI_PWM_CLOCK_DIVIDER_128  = 128,  //150khz
+    // RPI_PWM_CLOCK_DIVIDER_64   = 64,   //300khz
+    // RPI_PWM_CLOCK_DIVIDER_32   = 32,   //600.0khz
+    // RPI_PWM_CLOCK_DIVIDER_16   = 16,   //1.2Mhz
+    // RPI_PWM_CLOCK_DIVIDER_8    = 8,    //2.4Mhz
+    // RPI_PWM_CLOCK_DIVIDER_4    = 4,    //4.8Mhz
+    // RPI_PWM_CLOCK_DIVIDER_2    = 2,    //9.6Mhz, fastest you can get
+    // RPI_PWM_CLOCK_DIVIDER_1    = 1     //4.6875khz, same as divider 4096
+
+    // Configure PWM clock = 19.2Mhz / 32 = 600kHz
+    pwm_set_clock(32);
+
+    // Set PWM Frequency = 19.2Mhz / 16 / 1000 = 600Hz
+    pwm_set_range(0, 1000);
+
+    // Set PWM duty cycle as 800 / 1000 = 80%
+    pwm_set_data(0, 800);
 
     return 0;
 }
-

src/rpi/pwm.c

@@ -2,10 +2,11 @@
 volatile rpi_pwm_t *rpi_pwm;
 volatile rpi_pwm_clk_t* rpi_pwm_clk;
 
-void pwm_init(Rpi_Pwm_Channel channel, uint8_t markspace, uint8_t enable)
+int pwm_init(Rpi_Pwm_Channel channel, uint8_t markspace, uint8_t enable)
 {
     if(rpi_pwm == MAP_FAILED || rpi_pwm_clk == MAP_FAILED)
-        return;
+        return -1;
+
     if(channel == RPI_PWM_CHANNEL_0){
         if (markspace) {
             rpi_pwm->CTL.reg |=  RPI_PWM_CTL_PWEN1_Msk;
@@ -29,6 +30,7 @@ void pwm_init(Rpi_Pwm_Channel channel, uint8_t markspace, uint8_t enable)
             rpi_pwm->CTL.reg &= ~RPI_PWM_CTL_MSEN2_Msk;
         }
     }
+    return 0;
 }
 
 void pwm_set_clock(uint32_t divisor)
@@ -46,7 +48,7 @@ void pwm_set_clock(uint32_t divisor)
     rpi_pwm_clk->DIV.reg = RPI_PWM_PASSWD | (divisor << 12);
 
     rpi_pwm_clk->CTL.reg = RPI_PWM_PASSWD | 0x11;
-  
+
 }
 
 void pwm_set_range(Rpi_Pwm_Channel channel, uint32_t range)

src/rpi/pwm.h

@@ -138,7 +138,7 @@ extern volatile rpi_pwm_clk_t *rpi_pwm_clk;
 #ifdef __cplusplus
 extern "C" {
 #endif
-    void pwm_init(Rpi_Pwm_Channel channel, uint8_t markspace, uint8_t enable);
+    int pwm_init(Rpi_Pwm_Channel channel, uint8_t markspace, uint8_t enable);
 
     void pwm_set_clock(uint32_t divisor);
 

src/rpi/rpi.h

@@ -20,7 +20,7 @@
 #define RPI_GPIO_BASE          0x200000
 #define RPI_SYS_TIMER          0x3000
 #define RPI_PWM                0x20C000
-#define RPI_PWM_CLK	       0x1010a0
+#define RPI_PWM_CLK	           0x1010a0
 #define RPI_I2C0               0x205000
 #define RPI_I2C1               0x804000
 #define RPI_SPI0               0x204000