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fix: parse CRSF battery as big-endian per protocol spec

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CRSF battery frame is big-endian: voltage(u16 BE 0.1V),
current(u16 BE 0.1A), capacity(u24 BE mAh), remaining(u8 %).

Previous code read little-endian with wrong byte count (7 vs 8)
and wrong scaling (/1000 vs /10), producing 9.98V for a 1S battery.
This commit is contained in:
portersky
2026-06-14 23:34:12 +02:00
parent ef5012b9d4
commit d67d9b29d2
4 changed files with 39 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files
celrs/crsf_telemetry.c
+20 -8
View File
@@ -2,10 +2,20 @@
#include <string.h>
/* Helper: read uint16_t little-endian from buffer */
static uint16_t read_u16(uint8_t const* buf) {
static uint16_t read_u16_le(uint8_t const* buf) {
return (uint16_t)buf[0] | ((uint16_t)buf[1] << 8);
}
/* Helper: read uint16_t big-endian from buffer */
static uint16_t read_u16_be(uint8_t const* buf) {
return ((uint16_t)buf[0] << 8) | (uint16_t)buf[1];
}
/* Helper: read uint32_t big-endian from 3-byte buffer */
static uint32_t read_u24_be(uint8_t const* buf) {
return ((uint32_t)buf[0] << 16) | ((uint32_t)buf[1] << 8) | (uint32_t)buf[2];
}
int cel_crsf_telemetry_parse(cel_crsf_frame const* frame,
cel_telemetry* out) {
if (frame == NULL || out == NULL) return -1;
@@ -32,26 +42,28 @@ int cel_crsf_telemetry_parse(cel_crsf_frame const* frame,
}
case CEL_CRSF_TYPE_BATTERY: {
if (len < 7) return -1;
if (len < 8) return -1;
out->type = CEL_TELEM_BATTERY;
out->data.battery.voltage_mv = read_u16(p);
out->data.battery.current_ma = read_u16(p + 2);
out->data.battery.capacity_mah = read_u16(p + 4);
out->data.battery.remaining_pct = p[6];
/* CRSF battery: voltage(u16 BE 0.1V), current(u16 BE 0.1A),
capacity(u24 BE mAh), remaining(u8 %) */
out->data.battery.voltage_x10 = read_u16_be(p);
out->data.battery.current_x10 = read_u16_be(p + 2);
out->data.battery.capacity_mah = read_u24_be(p + 4);
out->data.battery.remaining_pct = p[7];
return 0;
}
case CEL_CRSF_TYPE_HEARTBEAT: {
if (len < 2) return -1;
out->type = CEL_TELEM_HEARTBEAT;
out->data.heartbeat.origin_addr = read_u16(p);
out->data.heartbeat.origin_addr = read_u16_le(p);
return 0;
}
case CEL_CRSF_TYPE_AIRSPEED: {
if (len < 2) return -1;
out->type = CEL_TELEM_AIRSPEED;
out->data.airspeed.speed_kmh = read_u16(p);
out->data.airspeed.speed_kmh = read_u16_le(p);
return 0;
}
celrs/crsf_telemetry.h
+4 -4
View File
@@ -36,11 +36,11 @@ typedef struct {
int16_t vertical_speed_cms;
} cel_telem_vario;
/* Battery sensor */
/* Battery sensor (CRSF: u16 BE 0.1V, u16 BE 0.1A, u24 BE mAh, u8 %) */
typedef struct {
uint16_t voltage_mv; /* millivolts */
uint16_t current_ma; /* milliamps */
uint16_t capacity_mah; /* mAh consumed */
uint16_t voltage_x10; /* x 0.1V */
uint16_t current_x10; /* x 0.1A */
uint32_t capacity_mah; /* mAh consumed */
uint8_t remaining_pct; /* percentage remaining */
} cel_telem_battery;
tests/test_crsf_telemetry.c
+12 -8
View File
@@ -60,13 +60,15 @@ void test_parse_link_stats_short(void) {
void test_parse_battery(void) {
uint8_t buf[32];
uint8_t payload[7] = {
0x40, 0x03, /* voltage: 0x0340 = 832 -> 0.832V */
0x00, 0x00, /* current: 0 */
0x00, 0x00, /* capacity: 0 */
/* CRSF battery: voltage(u16 BE 0.1V), current(u16 BE 0.1A),
capacity(u24 BE mAh), remaining(u8 %) = 8 bytes */
uint8_t payload[8] = {
0x03, 0xE8, /* voltage: 0x03E8 = 1000 -> 100.0V (10S LiPo) */
0x00, 0x64, /* current: 0x0064 = 100 -> 10.0A */
0x00, 0x03, 0xE8, /* capacity: 0x0003E8 = 1000mAh */
0x64 /* remaining: 100% */
};
build_frame(buf, 0x08, CEL_CRSF_TYPE_BATTERY, payload, 7);
build_frame(buf, 0x08, CEL_CRSF_TYPE_BATTERY, payload, 8);
cel_crsf_frame frame;
TEST_ASSERT_EQUAL_INT(0, cel_crsf_frame_parse(&frame, buf, sizeof(buf)));
@@ -74,13 +76,15 @@ void test_parse_battery(void) {
cel_telemetry telem;
TEST_ASSERT_EQUAL_INT(0, cel_crsf_telemetry_parse(&frame, &telem));
TEST_ASSERT_EQUAL_UINT(CEL_TELEM_BATTERY, telem.type);
TEST_ASSERT_EQUAL_UINT16(0x0340, telem.data.battery.voltage_mv);
TEST_ASSERT_EQUAL_UINT16(0x03E8, telem.data.battery.voltage_x10);
TEST_ASSERT_EQUAL_UINT16(0x0064, telem.data.battery.current_x10);
TEST_ASSERT_EQUAL_UINT32(0x0003E8, telem.data.battery.capacity_mah);
TEST_ASSERT_EQUAL_UINT8(0x64, telem.data.battery.remaining_pct);
}
void test_parse_heartbeat(void) {
uint8_t buf[32];
uint8_t payload[2] = {0x10, 0x80}; /* origin_addr = 0x8010 */
uint8_t payload[2] = {0x10, 0x80}; /* origin_addr LE = 0x8010 */
build_frame(buf, 0x10, CEL_CRSF_TYPE_HEARTBEAT, payload, 2);
cel_crsf_frame frame;
@@ -94,7 +98,7 @@ void test_parse_heartbeat(void) {
void test_parse_airspeed(void) {
uint8_t buf[32];
uint8_t payload[2] = {0x00, 0x01}; /* speed = 0x0100 = 256 km/h */
uint8_t payload[2] = {0x00, 0x01}; /* speed LE = 0x0100 = 256 km/h */
build_frame(buf, 0x08, CEL_CRSF_TYPE_AIRSPEED, payload, 2);
cel_crsf_frame frame;
tools/telemetry.c
+3 -3
View File
@@ -174,8 +174,8 @@ static void dashboard_update(dashboard_t* d, cel_telemetry const* telem,
break;
case CEL_TELEM_BATTERY:
d->has_batt = 1;
d->batt_v = telem->data.battery.voltage_mv / 1000.0f;
d->batt_a = telem->data.battery.current_ma / 1000.0f;
d->batt_v = telem->data.battery.voltage_x10 / 10.0f;
d->batt_a = telem->data.battery.current_x10 / 10.0f;
d->batt_mah = telem->data.battery.capacity_mah;
d->batt_pct = telem->data.battery.remaining_pct;
d->batt_t = now;
@@ -286,7 +286,7 @@ static void render_dashboard(dashboard_t const* d,
if (d->batt_v > 3.0f) ansi_green(); else ansi_red();
printf("%.2fV ", d->batt_v);
ansi_reset();
printf("%.1fA %dmah %d%%", d->batt_a, d->batt_mah, d->batt_pct);
printf("%.1fA %umah %d%%", d->batt_a, d->batt_mah, d->batt_pct);
print_age(now, d->batt_t);
} else {
ansi_dim(); printf("waiting..."); ansi_reset();