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[KenB]

Stephen, Baz,

Upon reflection I think it would be wise to augment the command format at this stage - so as to allow for sub-addressing and longer arguments. However I'm reluctant to make it too unwieldy.

May I suggest the following format

Leading character   - this can be A-Z, a-z or most of the ascii punctuation characters including @ # ? ! etc
Sub-address           - in the range 0 to 255
delimiter                - use a comma  (marks the end of the sub-address field)
Argument              - a 16 bit integer in the range 0-65535
                           - further arguments could be added here separated by commas
CR/LF                    - marks the end of the Argument field and the end of the command

A parser would be needed that strips off the various fields and feeds them to the command executor.  Remember that we need to fit this into a few kB, so that it doesn't take too much overhead.

The simplest commands could be just the leading character followed by the sub-address.


any thoughts?


Ken

[stephendv]

I think that's nailed it.  So one can use optional arguments if required, and if you just need to read a value then a simple 2 character command will do it.
For my SMS parser I ended up using the string library 'cause it was the fastest route to something that works, but yes, for a nicely optimised solution you'd probably want to build a character parser.

[Baz]

Yes that extra leading character adds long term expandability. You don't need the delimiter as you are character counting so it complicates both command creation and parsing. Only use <CR> not <CRLF> but make <LF> benign, ie always ignored, and <CR> both terminator and reset the parser. Hence you can hit <cr> a few times without effect just like you do on any console.
Make the reply message end with <CR> as most terminals add the LF anyway. Were you thinking of echoing the text message or the original command?
Sorry if I'm stating the obvious. All pretty standard stuff in the seventies - I can probably dig out an example in 6800 machine code if I can find the paper tape.

[stephendv]

I think you would still need the delimiter because the sub address can be 1 to 3 digits long, and also because their can be any number of arguments.

[Baz]

I was assuming the sub address was a single byte to give 0-255. Ken, you're going to have to write a full RFC now, maybe you can get EU funding!

[KenB]

Guys,

I've modified the code so that it now interprets  Command Sub_address,Argument1,Argument2  CR

The sub_address is 0-255, and arg1 and arg2 are 0-65535  but this can readily be changed to suit the application

If you don't put anything in arg1 and arg2 it returns them as zero.

So b1   is decoded as b 1,0,0

b254,65534,32768   becomes b 254,65534,32768

However there appears to be a bizzarre bug in the code/compiler, such that if you try to print out the char variable which holds the command, it sets it to zero, so you can't use it again.


Please PM me if you want a copy of the code



Ken