SDK Development / mbed-src

mbed SDK library sources

Fork of mbed-src by mbed official

Development branch of the mbed library sources. This library is kept in synch with the latest changes from the mbed SDK and it is not guaranteed to work.

If you are looking for a stable and tested release, please import one of the official mbed library releases:

Import librarymbed

The official Mbed 2 C/C++ SDK provides the software platform and libraries to build your applications.

Last commit 20 Feb 2019 by mbed official

Files at this revision

API Documentation at this revision

Revision 63:a46ad637dc84, committed 2013-12-19

Comitter:
mbed_official
Date:
Thu Dec 19 09:00:06 2013 +0000
Parent:
62:7731d679ae64
Child:
64:7b352733b00a
Commit message:
Synchronized with git revision f56cbfa53e8855c85dcdf19722a3080a3ad98ddc

Full URL: https://github.com/mbedmicro/mbed/commit/f56cbfa53e8855c85dcdf19722a3080a3ad98ddc/

fix 16bit timer pwm output

Changed in this revision

targets/hal/TARGET_NXP/TARGET_LPC11UXX/pwmout_api.c Show annotated file Show diff for this revision Revisions of this file 
--- a/targets/hal/TARGET_NXP/TARGET_LPC11UXX/pwmout_api.c	Tue Dec 17 11:00:05 2013 +0000
+++ b/targets/hal/TARGET_NXP/TARGET_LPC11UXX/pwmout_api.c	Thu Dec 19 09:00:06 2013 +0000
@@ -66,8 +66,6 @@
     LPC_CT32B0, LPC_CT32B1
 };
 
-static unsigned int pwm_clock_mhz;
-
 void pwmout_init(pwmout_t* obj, PinName pin) {
     // determine the channel
     PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
@@ -92,8 +90,6 @@
     /* Reset Functionality on MR3 controlling the PWM period */
     timer->MCR = 1 << 10;
     
-    pwm_clock_mhz = SystemCoreClock / 1000000;
-    
     // default to 20ms: standard for servos, and fine for e.g. brightness control
     pwmout_period_ms(obj, 20);
     pwmout_write    (obj, 0);
@@ -141,11 +137,18 @@
 // Set the PWM period, keeping the duty cycle the same.
 void pwmout_period_us(pwmout_t* obj, int us) {
     int i = 0;
-    uint32_t period_ticks = pwm_clock_mhz * us;
+    uint32_t period_ticks = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
     
     timer_mr tid = pwm_timer_map[obj->pwm];
     LPC_CTxxBx_Type *timer = Timers[tid.timer];
     uint32_t old_period_ticks = timer->MR3;
+
+    // for 16bit timer, set prescaler to avoid overflow
+    uint16_t high_period_ticks = period_ticks >> 16; 
+    if ((high_period_ticks) && (timer == LPC_CT16B0 || timer == LPC_CT16B1)) {
+        timer->PR = high_period_ticks;
+        period_ticks /= (high_period_ticks + 1);
+    }
     
     timer->TCR = TCR_RESET;
     timer->MR3 = period_ticks;
@@ -169,13 +172,14 @@
 }
 
 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
-    uint32_t t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
     timer_mr tid = pwm_timer_map[obj->pwm];
     LPC_CTxxBx_Type *timer = Timers[tid.timer];
+    uint32_t t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000 / (timer->PR + 1));
     
     timer->TCR = TCR_RESET;
     if (t_on > timer->MR3) {
         pwmout_period_us(obj, us);
+        t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000 / (timer->PR + 1));
     }
     uint32_t t_off = timer->MR3 - t_on;
     timer->MR[tid.mr] = t_off;