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Optimization: do not calc CRC for block1 again in rf_data_link_layer

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This commit is contained in:
Nanosonde 2020-11-10 14:37:57 +01:00
parent 007742483a
commit 12ffd1e86b
1 changed files with 9 additions and 1 deletions
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10
src/knx/rf_data_link_layer.cpp
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@ -98,9 +98,16 @@ void RfDataLinkLayer::frameBytesReceived(uint8_t* rfPacketBuf, uint16_t length)
return;
}
#if defined(DeviceFamily_CC13X0)
// Small optimization:
// We do not calculate the CRC16-DNP again for the first block.
// It was already done in the CC13x0 RX driver during reception.
// Also the two fixed bytes 0x44 and 0xFF are also there.
// So if we get here we can assume a valid block 1
#else
// CRC16-DNP of first block is always located here
uint16_t block1Crc = rfPacketBuf[10] << 8 | rfPacketBuf[11];
// If the checksum was ok and the other
// two constant header bytes match the KNX-RF spec. (C-field: 0x44 and ESC-field: 0xFF)...
// then we seem to have a valid first block of an KNX RF frame.
@ -108,6 +115,7 @@ void RfDataLinkLayer::frameBytesReceived(uint8_t* rfPacketBuf, uint16_t length)
if ((rfPacketBuf[1] == 0x44) &&
(rfPacketBuf[2] == 0xFF) &&
(crc16Dnp(rfPacketBuf, 10) == block1Crc))
#endif
{
// bytes left from the remaining block(s)
uint16_t bytesLeft = length - 12;