CODEWITHSUNDEEP
cserial-port
MadsChristiansen
MadsChristiansen

Reputation: 13

Serial data parsing

I have a probably simple question, which I just cant seem to understand.

I am creating a serial parser for a datalogger which sends a serial stream. Under the documentation for the product a calculation is stated, which I don't understand.

Lateral = Data1 And 0x7F + Data2 / 0x100
If (Data1 And 0x80)=0 Then Lateral = -Lateral

What does Data1 And 0x7f means? I know that 7F is 127, but besides that I don't understand the combination with the And statement.

What would the real formula look like?

Upvotes: 0

Views: 251

Answers (2)

Koushik Shetty
Koushik Shetty

Reputation: 2176

1st sentence Lateral = Data1 And(&) 0x7f + Data2/ 0x100

means take the magnitude of Data1(Data and 0x7f) and add to it the value of Data2/256

2nd sentence check the sign od Data1 and assign the same to Lateral.

Upvotes: 0

svk
svk

Reputation: 5919

Bitwise AND -- a bit in the output is set if and only if the corresponding bit is set in both inputs.

Since your tags indicate that you're working in C, you can perform bitwise AND with the & operator.

(Note that 0x7F is 01111111 and 0x80 is 10000000 in binary, so ANDing with these correspond respectively to extracting the lower seven bits and extracting the upper bit of a byte.)

Upvotes: 1

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