How to add caracter NULL in minimalmodbus.write_string() ?

[patfrench]

Hi,

I try to place a null caracter terminator in

write_string(0x1402,"SIMTRO698\0",6)

is it possible ?

Thank you

[j123b567]

Did you try it already? Do you have any issues?

You are writing 6 registers but your string is 5 registers log, so it will be padded by spaces as stated in documentation. If you need it to be padded by zeros, you should use "SIMTRO698\0\0\0"

[patfrench]

Hi,

I have no problem with write_string(0x1402,"SIMTRO698",5)

my problem is that the terminal character must be 0 (NULL in ASCII) I want to write the terminal character in the 6th register I will try your solution.

why three \0 ?

"SIMTRO698\0\0\0"

Thank you for answering so quickly

[j123b567]

Please, count number of characters first. SIMTRO698 is 9 characters but you are writing 5 registers, which mean 10 characters. As the documentation of write_string states. Your string will be padded with spaces. So in your case, just use write_string(0x1402,"SIMTRO698\0",5) If you need to set also the 6th register, then you should define also its content, if spaces are not good for you, so this is the meaning of additional two \0. So the alternative is write_string(0x1402,"SIMTRO698\0\0\0", 6).

[patfrench]

oups i'm sorry :( my str is "SIMTROF698" 0x1402 => 'SI' 0x1403 => 'MT' 0x1404 => 'RO' 0x1405 => 'F6' 0x1406 => '98' 0x1407 => caracter terminator = NUL

[j123b567]

So then write_string(0x1402,"SIMTROF698\0", 6) should just work

Or if you need to fill entire the last register write_string(0x1402,"SIMTROF698\0\0", 6)

[patfrench]

hi, perfect !!!! it's good

thank you for your support

[j123b567]

Your welcome. Please, close the issue if it is solved.