How can I publish hexadecimal values?

asked 2011-07-06 06:21:18 -0500

Khiya
49 ●9 ●10 ●15

updated 2011-07-07 15:19:58 -0500

Eric Perko

8406 ●73 ●90 ●144 http://ericperko.com/

Hello,

I haven't been able to find this on the ROS wiki: If I would like to create a publisher for hexadecimal, what type of message would I use? Specifically, I would like to publish this list to the \commands topic:

0x00 0x01 0x1F 0x7F

. I would then write a subscriber to \commands that took the hex values and sent them one by one to a serial port, where my motor controller understood them as motor commands and acted accordingly. I don't think they would publish under int32, would they?

Thanks,

Khiya

answered 2011-07-06 06:38:35 -0500

seanarm

723 ●38 ●51 ●63 http://seanmatthe.ws/

updated 2011-07-06 06:39:25 -0500

You could create a custom message that contains:

uint8[] commands

where 'commands' would contain your sequence of bytes.

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Comments

Thanks. So there's no simple way of publishing hex numbers on a ROS topic?

Khiya ( 2011-07-06 07:20:40 -0500 )edit

I don't think you can get much simpler than this.

arebgun ( 2011-07-06 07:47:57 -0500 )edit

Thanks a lot then!

Khiya ( 2011-07-07 01:47:30 -0500 )edit

@Khiya, any number can be hex. It's just a matter of interpreting/printing it that way. It's actually sent across as binary of course. rostopic echo interprets it as a decimal number if it's an int, but you could just as easily print it as hex with `printf( "%x", value );`

Asomerville ( 2011-07-07 16:11:27 -0500 )edit

Again, thanks you all. It hadn't quite clicked that hex is always just a sort of shorthand for binary. I appreciate your patience!

Khiya ( 2011-07-11 03:40:26 -0500 )edit

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