Decoding Information from Sparkfun Can Shield

Using Arduino Programming Questions
1

I´ve bought a Sparkfun Can-Shield some time ago and I´m trying to get some information from the Can bus (only read). I plugged it into the Car and got some information from the bus. I googled and found out that the information I want to get begins at Byte 5 and goes 10 Bit long. The Problem here is that the information I get is in HEX-Format and I have to split it to make it fit to the length. The information I get looks like this:

ID: 50B, Data: 19 8C 0 B4 94 13 0 A7

So for Byte 5 I have to start reading at 94 and then stop at the first 2 bit of 0. Now my question is how can I split the 0 so I can just get these 2 Bit and how can I decode the information after I get this. Here decode: 94 13 0?

Maybe there is a way to just get the binary information from the shield?

Thank you for the help!

2

All the data you receive is binary!!!!

It's only displayed as HEX as this is how your code is outputing the received data.

benipro:
I googled and found out that the information I want to get begins at Byte 5 and goes 10 Bit long.

please share the link or the whole information that explained how the data is supposedly represented.

btw if it 10 bits, I would expect it be across byte 5 and byte6 or byte 4 and byte5

benipro:
Here decode: 94 13 0?

that's 3 bytes!!!! ??

3

Look in the reference section here. There's a section towards the bottom called bitwise operators. You can extract and combine the bits you need with bitwise and, bitwise or and shift.

4

@sherzaad you are completely right, I made a mistake in my question. So the information is going across Byte 5 and 6 and therefore the information I think is: 13 0

To your answer about the binary stuff.
Do you know how I can get access to the bits so I can convert them to a decimal number ?
because I printed them out several times but I only receive these HEX numbers.

Thank you for the fast replys!

5

Btw. I´m using the code based on the tutorial from sparkfun. So I get a tCan-Message back.

6

benipro:
13 0

in the above, do you know which byte has the MSbit and LS bit?

I mean Byte 5 and 6 are 8 bit wide (so 16 bits in all)

so where is bit 0 and bit 9 located within those bytes for your data?

you did not supply that information!!!! (and I previously asked more info on that!)

7

The information starts with the MSB at beginning of the Byte 5 (at Bit 0) and ends after the first 2 of byte 6.

8

benipro:
The information starts with the MSB at beginning of the Byte 5 (at Bit 0) and ends after the first 2 of byte 6.

ok...

so in pseudocode something like this maybe:

union { 
    uint16_t val; 
    uint8_t bytes[2]
} data;
	
data.bytes[0] = Byte5 //lower byte
data.bytes[1] = Byte6 //upper byte
	
uint16_t myData = data.val & 0x03FF //0x03FF = 10 bit mask
9

I think your code could work but I don't quite get this line:

uint16_t myData = data.val & 0x03FF //0x03FF = 10 bit mask

Because in the definition it stands it would do something like:
e.g.
0110001000
0001001100
=>0000001000

10

data.val is a 16 bit variable

the mask basically set bits 10-15 to zero so that all you are left with is your 10 bit data.

11

That makes sense!

Thank you very much for your patience and the answers they helped a lot!