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DualCam Communication Protocol (view source)
Revision as of 07:02, 24 August 2022
, 07:02, 24 August 2022→CRC-16 calculation
The algorithm how to calculate CRC - 16(also known as CRC - 16 / IBM) you will find below.
The algorithm how to calculate CRC - 16(also known as CRC - 16 / IBM) you will find below.
var crc = {
var crc = {
extractCRC: function (message) {
extractCRC: function (message) {
crcData = message.slice(message.length - 2, message.length);
crcData = message.slice(message.length - 2, message.length);
let idx = 0;
let idx = 0;
let crc = 0x0000;
let crc = 0x0000;
/* the payload length is calculated with removing size of header and CRC (4 + 2 bytes) */
/* the payload length is calculated with removing size of header and CRC (4 + 2 bytes) */
let payload_length = message.length - 6;
let payload_length = message.length - 6;
/* the payload is separated from the message header and CRC (4 bytes ofset + length)*/
/* the payload is separated from the message header and CRC (4 bytes ofset + length)*/
let payload = message.slice(4, 4 + payload_length);
let payload = message.slice(4, 4 + payload_length);
/* Init value for the first message is zero and for the upcoming messages it is the CRC value of the previous message */
/* Init value for the first message is zero and for the upcoming messages it is the CRC value of the previous message */
crc = previous_crc;
crc = previous_crc;
for (idx = 0; idx < payload_length; idx++) {
for (idx = 0; idx < payload_length; idx++) {
let bit;
let bit;
/* Use XOR operation for initial value and payload */
/* Use XOR operation for initial value and payload */
crc ^= payload[idx];
crc ^= payload[idx];
for (bit = 0; bit < 8; bit++) {
for (bit = 0; bit < 8; bit++) {
let carry_bit = crc & 0x01;
let carry_bit = crc & 0x01;
crc >>= 0x01;
crc >>= 0x01;
if (carry_bit != 0) {
if (carry_bit != 0) {
crc ^= crc_poly;
crc ^= crc_poly;
}
}
}
}
}
}
return crc;
return crc;
}
}
};
};
exports.crc = crc;
exports.crc = crc;
==File transfer visual flow==
==File transfer visual flow==