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...GCR is crazy

This commit is contained in:
Wastl Kraus 2025-09-01 21:26:22 +02:00
parent 759b7ef63c
commit 99a694cbef
2 changed files with 16 additions and 8 deletions
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23
DShotRMT.cpp
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@ -281,6 +281,15 @@ dshot_packet_t DShotRMT::_buildDShotPacket(const uint16_t value)
// Init packet structure
dshot_packet_t packet = {};
// Re-check for valid value
if (value > DSHOT_THROTTLE_MAX)
{
_dshot_log(PACKET_BUILD_ERROR);
// Something is really wrong
return packet;
}
// Build packet
packet.throttle_value = value;
packet.telemetric_request = _is_bidirectional ? 1 : 0;
@ -414,18 +423,16 @@ uint16_t DShotRMT::_decodeDShotFrame(const rmt_symbol_word_t *symbols)
raw_gcr_data = (raw_gcr_data << 1) | bit_is_one;
}
// Decode the GCR data to get the original 10-bit value
uint16_t decoded_value = 0;
for (int i = 0; i < 10; i++)
{
decoded_value = (decoded_value << 1) | ((raw_gcr_data >> (10 - 1 - i)) & 1);
}
// GCR decoding over the "throttle" bits
// GCR encoding rule is: bit_n = gcr_bit_n ^ gcr_bit_(n-1)
uint16_t gcr_data = (raw_gcr_data >> 5) & 0b000000001111111111;
uint16_t received_data = gcr_data ^ (gcr_data >> 1);
// Extract CRC from gcr answer
uint16_t received_crc = raw_gcr_data & 0b0000000000001111;
// Calculate expected CRC using the new, centralized function
uint16_t data_for_crc = (decoded_value << 1) | 1; // Telemetry request bit is always 1 for bidirectional
uint16_t data_for_crc = (received_data << 1) | 1; // Telemetry request bit is always 1 for bidirectional
uint16_t calculated_crc = _calculateCRC(data_for_crc);
// Validate CRC
@ -436,7 +443,7 @@ uint16_t DShotRMT::_decodeDShotFrame(const rmt_symbol_word_t *symbols)
}
// The data is eRPM * 100
return decoded_value;
return received_data;
}
// Check if enough time has passed for next transmission

1
DShotRMT.h
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@ -181,4 +181,5 @@ private:
static constexpr std::string_view COMMAND_NOT_VALID = "Not a valid DShot Command (0 - 47)!";
static constexpr std::string_view BIDIR_NOT_ENABLED = "Bidirectional DShot support not enabled!";
static constexpr std::string_view RX_RMT_RECEIVER_ERROR = "RX RMT receiver error!";
static constexpr std::string_view PACKET_BUILD_ERROR = "Value too big for DShot Packet!";
};