Hardware PWM on two channels causes initialisation glitch about pigpio

[joan2937]

At the moment changing one channel will cause a glitch on the other channel if it is also transmitting PWM.

I'll have a look at the datasheet to see if the glitch can be prevented.

[joan2937]

I changed the title to more accurately reflect the actual behaviour.

I have been more intelligent in the way I set up the channels which means this should no longer happen.

The fix will be in V52 (when it is released).

[nachoplus]

Ok. I'll be waiting for V52. I'll give you feedback when I try it.
Thank you very much! I really apreciate your fast support!

[joan2937]

If you want to give it a try you could apply the following patch to V51 of pigpio.c.

Save as patch.txt and then

patch pigpio.c patch.txt

--- pigpio.c-V51    2016-04-26 17:42:48.539091253 +0100
+++ pigpio.c    2016-04-26 16:51:39.450230475 +0100
@@ -25,7 +25,7 @@
 For more information, please refer to <http://unlicense.org/>
 */

-/* pigpio version 51 */
+/* pigpio version 52 */

 /* include ------------------------------------------------------- */

@@ -1144,6 +1144,7 @@
 static uint32_t reportedLevel = 0;

 static int waveClockInited = 0;
+static int PWMClockInited = 0;

 static volatile gpioStats_t gpioStats;

@@ -7551,6 +7552,7 @@
    DBG(DBG_STARTUP, "");

    waveClockInited = 0;
+   PWMClockInited = 0;

    clock_gettime(CLOCK_REALTIME, &libStarted);

@@ -8958,6 +8960,7 @@
       stopHardwarePWM();
       initClock(0); /* initialise secondary clock */
       waveClockInited = 1;
+      PWMClockInited = 0;
    }

    p = rawWaveCBAdr(waveInfo[wave_id].topCB);
@@ -9194,6 +9197,7 @@
       stopHardwarePWM();
       initClock(0); /* initialise secondary clock */
       waveClockInited = 1;
+      PWMClockInited = 0;
    }

    dmaOut[DMA_CS] = DMA_CHANNEL_RESET;
@@ -11413,11 +11417,16 @@
       old_PWM_CTL = pwmReg[PWM_CTL] &
          (PWM_CTL_PWEN1 | PWM_CTL_MSEN1 | PWM_CTL_PWEN2 | PWM_CTL_MSEN2);

-      pwmReg[PWM_CTL] = 0;
+      if (!PWMClockInited)
+      {
+         pwmReg[PWM_CTL] = 0;

-      myGpioDelay(10);
+         myGpioDelay(10);

-      initHWClk(CLK_PWMCTL, CLK_PWMDIV, CLK_CTL_SRC_PLLD, 2, 0, 0);
+         initHWClk(CLK_PWMCTL, CLK_PWMDIV, CLK_CTL_SRC_PLLD, 2, 0, 0);
+
+         PWMClockInited = 1;
+      }

       if (pwm == 0)
       {

[nachoplus]

Clean compilation and works perfectly! This was a blocking issue for me and now I can continue with my project!
Thank you very much!

[joan2937]

Okay. Unless I hear otherwise I'll close this as an issue when I release V52.

[joan2937]

V52 released.