david.tahir/QuadMeUp_Crossbow
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Updated CRC method

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Pawel Spychalski
2017-11-15 11:14:15 +01:00
committed by Pawel Spychalski (DzikuVx)
parent 36dc76db0d
commit 9f48e0fd6f
2 changed files with 19 additions and 6 deletions
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2
README.md
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@@ -13,7 +13,7 @@ Development, ready for testing
| 1 | Channel ID | channel used for comunication between TX and RX | | 1 | Channel ID | channel used for comunication between TX and RX |
| 2 | Frame type & Length | bits 7-5 defines frame, bits 4-0 payload length | | 2 | Frame type & Length | bits 7-5 defines frame, bits 4-0 payload length |
| 3 - 34 | Payload | 32 bytes max | | 3 - 34 | Payload | 32 bytes max |
| payload length + 3 | CRC | XOR of all previous bytes | | payload length + 3 | CRC | using crc8_dvb_s2 method |
## Frame types ## Frame types

23
qsp.cpp
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@@ -49,9 +49,22 @@ uint8_t get10bitLowShift(uint8_t channel) {
return 8 - get10bitHighShift(channel); return 8 - get10bitHighShift(channel);
} }
uint8_t crc8_dvb_s2(uint8_t crc, uint8_t a)
{
crc ^= a;
for (int ii = 0; ii < 8; ++ii) {
if (crc & 0x80) {
crc = (crc << 1) ^ 0xD5;
} else {
crc = crc << 1;
}
}
return crc;
}
void qspComputeCrc(QspConfiguration_t *qsp, uint8_t dataByte) void qspComputeCrc(QspConfiguration_t *qsp, uint8_t dataByte)
{ {
qsp->crc ^= dataByte; qsp->crc = crc8_dvb_s2(qsp->crc, dataByte);
} }
void encodeRxHealthPayload(QspConfiguration_t *qsp, RxDeviceState_t *rxDeviceState, RadioState_t *radioState) { void encodeRxHealthPayload(QspConfiguration_t *qsp, RxDeviceState_t *rxDeviceState, RadioState_t *radioState) {
@@ -161,8 +174,8 @@ void qspDecodeIncomingFrame(
{ {
qsp->frameDecodingStartedAt = millis(); qsp->frameDecodingStartedAt = millis();
qsp->protocolState = QSP_STATE_CHANNEL_RECEIVED; qsp->protocolState = QSP_STATE_CHANNEL_RECEIVED;
qsp->crc = 0 ^ incomingByte; qsp->crc = 0;
qspComputeCrc(qsp, incomingByte);
qspClearPayload(qsp); qspClearPayload(qsp);
receivedPayload = 0; receivedPayload = 0;
@@ -175,7 +188,7 @@ void qspDecodeIncomingFrame(
else if (qsp->protocolState == QSP_STATE_CHANNEL_RECEIVED) else if (qsp->protocolState == QSP_STATE_CHANNEL_RECEIVED)
{ {
//Frame ID and payload length //Frame ID and payload length
qsp->crc ^= incomingByte; qspComputeCrc(qsp, incomingByte);
frameId = (incomingByte >> 4) & 0x0f; frameId = (incomingByte >> 4) & 0x0f;
payloadLength = incomingByte & 0x0f; payloadLength = incomingByte & 0x0f;
@@ -189,7 +202,7 @@ void qspDecodeIncomingFrame(
} }
//Now it's time for payload //Now it's time for payload
qsp->crc ^= incomingByte; qspComputeCrc(qsp, incomingByte);
qsp->payload[receivedPayload] = incomingByte; qsp->payload[receivedPayload] = incomingByte;
receivedPayload++; receivedPayload++;