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| author | Vincent Palatin <vpalatin@chromium.org> | 2013-06-10 17:43:42 -0700 |
|---|---|---|
| committer | ChromeBot <chrome-bot@google.com> | 2013-06-11 08:42:11 -0700 |
| commit | d7b9b2a088dcf129739c7a6b8a30bc292ea7234d (patch) | |
| tree | d8fbfca1b874c0ac69e5768bdfb324d47787d923 | |
| parent | efc560f04f292cb42bdaf81c0d4fa3b1f5a1482a (diff) | |
| download | chrome-ec-d7b9b2a088dcf129739c7a6b8a30bc292ea7234d.tar.gz | |
spring: update PWM characterization for DVT1
The new constants used to convert PWM duty cycle to input current,
based on a linear regression done on Aaron's characterization data
measured on DVT1 PCB.
The data points are linear enough to use the linear relationship
to set the current limitation.
Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BRANCH=spring
BUG=chrome-os-partner:19281
TEST=none
Change-Id: I8378aaea21d5b3229d505caf4849257ded77e1ad
Reviewed-on: https://gerrit.chromium.org/gerrit/58143
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>
| -rw-r--r-- | board/spring/usb_charging.c | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/board/spring/usb_charging.c b/board/spring/usb_charging.c index 277720c886..a6a73fdf36 100644 --- a/board/spring/usb_charging.c +++ b/board/spring/usb_charging.c @@ -41,12 +41,22 @@ /* Voltage threshold of D+ for video */ #define VIDEO_ID_THRESHOLD 1335 +/* + * Mapping from PWM duty to current: + * Current = A + B * PWM_Duty + */ +#define PWM_MAPPING_A 2958 +#define PWM_MAPPING_B (-29) + +/* Map current in milli-amps to PWM duty cycle percentage */ +#define MA_TO_PWM(curr) (((curr) - PWM_MAPPING_A) / PWM_MAPPING_B) + /* PWM controlled current limit */ -#define I_LIMIT_500MA 90 -#define I_LIMIT_1000MA 75 -#define I_LIMIT_1500MA 60 -#define I_LIMIT_2000MA 50 -#define I_LIMIT_2400MA 35 +#define I_LIMIT_500MA MA_TO_PWM(500) +#define I_LIMIT_1000MA MA_TO_PWM(1000) +#define I_LIMIT_1500MA MA_TO_PWM(1500) +#define I_LIMIT_2000MA MA_TO_PWM(2000) +#define I_LIMIT_2400MA MA_TO_PWM(2400) #define I_LIMIT_3000MA 0 /* PWM control loop parameters */ @@ -69,13 +79,6 @@ #define DELAY_USB_DP_DN_MS 20 #define DELAY_ID_MUX_MS 30 -/* - * Mapping from PWM duty to current: - * Current = A + B * PWM_Duty - */ -#define PWM_MAPPING_A 3012 -#define PWM_MAPPING_B (-29) - static int current_dev_type = TSU6721_TYPE_NONE; static int nominal_pwm_duty; static int current_pwm_duty; |