diff options
| author | Mulin Chao <mlchao@nuvoton.com> | 2016-08-12 11:34:15 +0800 |
|---|---|---|
| committer | chrome-bot <chrome-bot@chromium.org> | 2016-08-12 20:49:49 -0700 |
| commit | e0497b041ac077673ffa182a3cb0e39f7c0c0cf6 (patch) | |
| tree | d96bd448d9dbb82f48b7af3e94330b28dec8c16f | |
| parent | 31f297da0b9cb3b4e6fb1cc2f044f71df1c830c2 (diff) | |
| download | chrome-ec-e0497b041ac077673ffa182a3cb0e39f7c0c0cf6.tar.gz | |
npcx: Fixed pwm bug to improve deviation of PWM frequency.
According the formula for computing prescaler of PWM, we needn't minus
one again in line 89 of pwm.c. On npcx's evb, we observe the deviation
of PWM 1 which freq is 10K is reduced from 0.6 kHz to 0.01 kHz. We also
change PWM 1's freq to 100 Hz with PWM_CONFIG_DSLEEP and the deviation
is reduced from 64.2 Hz to 9.2Hz.
Modified sources:
1. pwm.c: Modifed formula for computing prescaler of PWM.
BRANCH=none
BUG=chrome-os-partner:56052
TEST=make BOARD=npcx_evb; use "pwm 1 50" to observe deviation of freq
Change-Id: I9cd7fc0d807df62083d49a7e9ec6de1d9028be1b
Signed-off-by: Mulin Chao <mlchao@nuvoton.com>
Reviewed-on: https://chromium-review.googlesource.com/368560
Reviewed-by: Shawn N <shawnn@chromium.org>
| -rw-r--r-- | chip/npcx/pwm.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/chip/npcx/pwm.c b/chip/npcx/pwm.c index 32f676aa27..0f30e3cad4 100644 --- a/chip/npcx/pwm.c +++ b/chip/npcx/pwm.c @@ -86,7 +86,7 @@ void pwm_set_freq(enum pwm_channel ch, uint32_t freq, uint32_t res) prescaler_divider = 0xFFFF; /* Configure computed prescaler and resolution */ - NPCX_PRSC(mdl) = (uint16_t)prescaler_divider - 1; + NPCX_PRSC(mdl) = (uint16_t)prescaler_divider; /* Set PWM cycle time */ NPCX_CTR(mdl) = res - 1; |