# Help figuring out a checksum algorithm

This is a discussion on Help figuring out a checksum algorithm within the A Brief History of Cprogramming.com forums, part of the Community Boards category; Hi all, I'm new to the board and I need help. I am trying to figure out a checksum algorithm. ...

1. ## Help figuring out a checksum algorithm

Hi all, I'm new to the board and I need help.
I am trying to figure out a checksum algorithm. from what I know it is a fairly simple alg but i still am having trouble.
Here is a sample of the data and the checksum:

F0 20 20 31 30 37 2E 37 20 46 4D 32 2E 34 20 20 20 and the Checksum is 3E

Another set of Data is
F0 43 44 20 30 31 20 20 1C 54 52 20 31 31 20 1C 1C and the Checksum is 3A
another is
F0 20 20 31 30 37 2E 37 20 46 4D 32 2E 35 20 20 20 and the checksum is 3D

Any help would be greatly appreciated.

2. Doesn't look like a C question to me.... over to GD we go...

3. What is the context? Where does the data/checksum come from? There are two reasons for asking.

1. Knowledge of the context may suggest a standard solution, and so we can help you.

2. If you are trying to hack something, then we will not!

If you have a legit problem here, post a few more details, and we'll see what we can do.

4. This is a signal from my car radio to my cars display system. I want to figure it out so I can display my own information to it.

5. Can you throw arbitrary input to the the display? Can you do stuff like change the least significant bit by just one?

6. What kind of car radio is it? Perhaps someone knows the protocol this radio uses. How did you know that the sample data was real sample data and the checksum is correct?