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feat: implement frame parse and streaming reader

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cel_crsf_frame_parse() parses ELRS USB format frames:
  [addr][length][type][payload...][crc]

cel_crsf_stream_* provides incremental parsing from a byte
stream: skips invalid sync bytes, discards bad CRC frames,
buffers partial frames across feed calls.
This commit is contained in:
portersky
2026-06-14 20:51:57 +02:00
parent dde27ab566
commit a846b063f9
5 changed files with 335 additions and 36 deletions
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tests/test_crsf.c
+84 -1
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@@ -18,7 +18,6 @@ void test_crc_single_byte(void) {
}
void test_crc_known_value(void) {
/* Verify CRC is deterministic */
uint8_t data[6] = {0x10, 0x80, 0x03, 0x02, 0x80, 0x01};
uint8_t crc = cel_crsf_crc(data, 6);
TEST_ASSERT_TRUE(crc != 0);
@@ -39,6 +38,83 @@ void test_channel_clamp_mid(void) {
TEST_ASSERT_EQUAL_INT16(CEL_CRSF_CH_MID, cel_crsf_channel_clamp(CEL_CRSF_CH_MID));
}
/* Frame parse tests — ELRS format: [addr][length][type][payload][crc] */
/* Build a valid test frame with known CRC */
static void build_test_frame(uint8_t* dst, uint8_t addr, uint8_t type,
uint8_t const* payload, uint8_t payload_len) {
uint8_t length = 1 + payload_len + 1; /* type + payload + crc */
dst[0] = addr;
dst[1] = length;
dst[2] = type;
memcpy(dst + 3, payload, payload_len);
uint8_t crc = cel_crsf_crc(dst + 2, 1 + payload_len);
dst[2 + length - 1] = crc;
}
void test_parse_valid_frame(void) {
uint8_t buf[32];
uint8_t payload[2] = {0x80, 0x01};
build_test_frame(buf, 0xC8, CEL_CRSF_TYPE_HEARTBEAT, payload, 2);
cel_crsf_frame frame;
TEST_ASSERT_EQUAL_INT(0, cel_crsf_frame_parse(&frame, buf, sizeof(buf)));
TEST_ASSERT_EQUAL_UINT8(0xC8, frame.addr);
TEST_ASSERT_EQUAL_UINT8(CEL_CRSF_TYPE_HEARTBEAT, frame.type);
TEST_ASSERT_EQUAL_UINT8(2, frame.payload_len);
TEST_ASSERT_EQUAL_UINT8(0x80, frame.payload[0]);
TEST_ASSERT_EQUAL_UINT8(0x01, frame.payload[1]);
}
void test_parse_null_frame(void) {
uint8_t buf[8];
TEST_ASSERT_EQUAL_INT(-1, cel_crsf_frame_parse(NULL, buf, 8));
}
void test_parse_null_buf(void) {
cel_crsf_frame frame;
TEST_ASSERT_EQUAL_INT(-1, cel_crsf_frame_parse(&frame, NULL, 8));
}
void test_parse_too_short(void) {
cel_crsf_frame frame;
uint8_t buf[2] = {0xC8, 0x03};
TEST_ASSERT_EQUAL_INT(-1, cel_crsf_frame_parse(&frame, buf, 2));
}
void test_parse_bad_crc(void) {
uint8_t buf[32];
uint8_t payload[2] = {0x80, 0x01};
build_test_frame(buf, 0xC8, CEL_CRSF_TYPE_HEARTBEAT, payload, 2);
buf[5] ^= 0xFF; /* corrupt the CRC */
cel_crsf_frame frame;
TEST_ASSERT_EQUAL_INT(-1, cel_crsf_frame_parse(&frame, buf, sizeof(buf)));
}
void test_parse_empty_payload(void) {
uint8_t buf[32];
build_test_frame(buf, 0xEE, CEL_CRSF_TYPE_HEARTBEAT, NULL, 0);
cel_crsf_frame frame;
TEST_ASSERT_EQUAL_INT(0, cel_crsf_frame_parse(&frame, buf, sizeof(buf)));
TEST_ASSERT_EQUAL_UINT8(0xEE, frame.addr);
TEST_ASSERT_EQUAL_UINT8(CEL_CRSF_TYPE_HEARTBEAT, frame.type);
TEST_ASSERT_EQUAL_UINT8(0, frame.payload_len);
}
void test_parse_module_addr(void) {
uint8_t buf[32];
uint8_t payload[4] = {0xAA, 0xBB, 0xCC, 0xDD};
build_test_frame(buf, 0xEE, CEL_CRSF_TYPE_GPS, payload, 4);
cel_crsf_frame frame;
TEST_ASSERT_EQUAL_INT(0, cel_crsf_frame_parse(&frame, buf, sizeof(buf)));
TEST_ASSERT_EQUAL_UINT8(0xEE, frame.addr);
TEST_ASSERT_EQUAL_UINT8(CEL_CRSF_TYPE_GPS, frame.type);
TEST_ASSERT_EQUAL_UINT8(4, frame.payload_len);
}
int main(void) {
UNITY_BEGIN();
RUN_TEST(test_crc_empty);
@@ -47,5 +123,12 @@ int main(void) {
RUN_TEST(test_channel_clamp_min);
RUN_TEST(test_channel_clamp_max);
RUN_TEST(test_channel_clamp_mid);
RUN_TEST(test_parse_valid_frame);
RUN_TEST(test_parse_null_frame);
RUN_TEST(test_parse_null_buf);
RUN_TEST(test_parse_too_short);
RUN_TEST(test_parse_bad_crc);
RUN_TEST(test_parse_empty_payload);
RUN_TEST(test_parse_module_addr);
return UNITY_END();
}