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fix: Use more efficient integer operations, ensure return values don'r get out of sync with the lookup table.

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MickiusMousius 2023-12-13 12:06:39 +10:30
parent d86d289d76
commit 73646cbfc7
1 changed files with 10 additions and 10 deletions
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20
app/module/drivers/sensor/battery/battery_common.c
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@ -36,8 +36,8 @@ uint8_t lithium_ion_mv_to_pct(int16_t batt_mv) {
// https://blog.ampow.com/lipo-voltage-chart/ // https://blog.ampow.com/lipo-voltage-chart/
// //
struct lookup_point { struct lookup_point {
float millivolts; int16_t millivolts;
float percent; int16_t percent;
}; };
static const struct lookup_point battery_lookup[] = { static const struct lookup_point battery_lookup[] = {
@ -46,20 +46,20 @@ uint8_t lithium_ion_mv_to_pct(int16_t batt_mv) {
{.millivolts = 3270, .percent = 0}, {.millivolts = 3270, .percent = 0},
}; };
if (batt_mv > 4200) { if (batt_mv > battery_lookup[0].millivolts) {
return 100; return battery_lookup[0].percent;
} }
for (int i = 1; i < ARRAY_SIZE(battery_lookup); i++) { for (int i = 0; i < ARRAY_SIZE(battery_lookup); i++) {
struct lookup_point one = battery_lookup[i - 1]; struct lookup_point one = battery_lookup[i - 1];
struct lookup_point two = battery_lookup[i]; struct lookup_point two = battery_lookup[i];
if (batt_mv >= two.millivolts) { if (batt_mv >= two.millivolts) {
float slope = (one.percent - two.percent) / (one.millivolts - two.millivolts); const int t = batt_mv - one.millivolts;
float offset = one.percent - slope * one.millivolts; const int dx = two.millivolts - one.millivolts;
float batt_percent = (slope * batt_mv) + offset; const int dy = two.percent - one.percent;
return (uint8_t)batt_percent; return one.percent + dy * t / dx;
} }
} }
return 0; return battery_lookup[ARRAY_SIZE(battery_lookup) - 1].percent;
} }