![]() ![]() I'd like to use a simple software check on the PIC32 that compares the PC's calculated checksum to the sRxPktStat->pktChecksum and abort receiving the packet but maybe also have the PIC32 send a response packet. How do you calculate a 2-byte checksum that will be inserted into the payload, which will be included in the computation of payload? It seems rather complicated and I just read that this checksum includes the FCS bytes which I don't know how to access or compute on the PC side when I send a frame. I'm not convinced it is possible but it must be. Subtract the values out makes sense if it is possible. I have been searching for subtracting values out but have not found any online resource that would help. I'd be interested in using pktChecksum found in sRxPktStat structure for a custom protocol where I embed a calculated checksum on the PC into the Ethernet frame's payload (at a custom location, one that is not specific to TCP or UDP) that gets sent to the PIC32. The calculator appends an Initial value for the CRC of 0xff so dont include a. Then it XORs the result with the third hexadecimal and gets the next result. We must then calculate the required remainder from a modulo-2 divide and add this to the data, in order that the remainder will be zero when we perform the divide. If we receive a remainder of zero, we can determine there are no errors. The XOR is commutative so it starts with the first two hexadecimal numbers, XORs them together, and gets the result. Cyclic Redundancy Check (CRC) With CRC we have a generator polynomial which will divide into a received value. This section mentions that the PKT_CHECKSUM field can be useful in TCP/IP software implementations. The checksum includes message Header, Length. Hex xor calculator tool What is a hex xor calculator This tool calculates the bitwise XOR operation of all input hex numbers. If software needs to exclude more bytes from the checksum, it must subtract the values out." I'm interested in Section 35.4.11.1 Payload Checksum Calculation and the sentences that mentions that "The payload checksum is calculated over the complete received packet except for the first 14 bytes (destination address, source address and length/type fields). Calculating the PIC32 Ethernet Payload Checksum ![]()
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