Sending Text to Hex in serial Port

Question

Jason 2022-4-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1694025-sending-text-to-hex-in-serial-port

评论： Walter Roberson 2022-4-11

Hello, I have managed to send hex commands to a pump using the serial port (that requires the commands to be in hex)

msg=[0xFF 0x2F 0x31 0x41 0x31  0x30 0x30 0x52 0x0D]
flush(device);          
write(device,msg,"uint8")

The Number thats part of the hex code above is 3000

i.e. the (0x33 0x30 0x30 0x30) part.

I am wanting to change the number at will i.e. 100, 500, 1000 etc, but dont want to hard code it.

I see the dec2hex can help

>> a=dec2hex('3000')
a =
'33'
'30'
'30'
'30'

But how to I put the output of the dec2hex into the format that I need in msg (i.e. prefix each one wit 0x and put a space inbetween)?

Thanks

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Answer 1

Walter Roberson 2022-4-11

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1694025-sending-text-to-hex-in-serial-port#answer_940445

在 MATLAB Online 中打开

msg=[0xFF 0x2F 0x31 0x41 0x31  0x30 0x30 0x52 0x0D]
msg = 1×9
   255    47    49    65    49    48    48    82    13

That does not create msg as a character vector with '0xFF<space>' and so on. Instead it converts the values to uint8. Look at the values:

whos msg
  Name      Size            Bytes  Class    Attributes

  msg       1x9                 9  uint8              
ans = 
    'ÿ/1A100R
     '

So you would do something like

msg_hdr = [0xFF 0x2F 0x31 0x41];
msg_trailer = [0x52 0x0D];
msg = [msg_hdr, uint8(num2str(VALUE)), msg_trailer];
write(device, msg, 'uint8');

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Jason 2022-4-11

Again out of curiosity, why are you using fprintf for the serial port and not write or writeline?

Walter Roberson 2022-4-11

在 MATLAB Online 中打开

%variation 1
y_umlaut = char(255);
carriage_return = char(13);   %not char(10)
msg = y_umlaut + "/1A" + VALUE + "R" + carriage_return;
write(device, msg, 'uint8')
%variation 2
configureTerminator(device, "CR");
y_umlaut = char(255);
msg = y_umlaut + "/1A" + VALUE + "R";
writeline(device, msg)
%variation 3
fprintf(device, '\o377/1A%dR\r', VALUE);
%variation 4
fprintf(device, '\xff/1A%dR\r', VALUE);