How do I know the Hexadecimal to use to communicate with my serial port?

Question

Background information: I am using Visual Studio 2005 to write MFC/C++ on a dialog box. Please pardon me if I lack out any information or anything essential to answer my questio

Answer 1

You will have to dig up the documentation for the device you are talking to. It should provide you with the protocol that's used to exchange data. Ask your colleagues about it, they surely know where that documentation is located.

I can only make rough guesses from

21 04 07 00 08 00 0F 22

The 0x21 byte is likely to be the start byte that indicates the start of the frame. The device uses it to synchronize itself in order to detect the start of a frame. The 0x22 byte is likely to be the end byte, a confirmation that no more bytes are expected to follow. The device uses it to know that the frame was received in full so it can process the data. The 0x04 byte is likely to be a length byte, it encodes how many data bytes follow. Which appear to be 0x07, 0x00, 0x08, 0x00. Pretty unguessable what they encode, it might be two 16-bit values for example, 7 and 8. The 0x0f byte is probably the checksum of the data bytes, used to verify that the data bytes were not corrupted.

Very rough guesses, read the documentation to know for sure. And of course talk to your colleagues about it, little point in asking a completely stranger on the Internet when you have people that know the facts in the cubicle next to yours. Petzold's book "Code" is pretty good to help you stop talking about "hex".