Hex manipulation - Printable Version

Hex manipulation - Printable Version

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+--- Thread: Hex manipulation (/showthread.php?tid=392)

Hex manipulation - buuuudzik - 18.09.2016

Hello,

maybe do you know functions for hex<->string conversion? I am preparing a full integration with Somfy blinds via RS485 and I want receive some data. After this I must delete last 2 bytes(checksum) and inverse all other bytes.

I've tried used this function which I've found in some forum:

Code:
function string.fromhex(str)

    return (str:gsub('..', function (cc)

        return string.char(tonumber(cc, 16))

    end))

end

function string.tohex(str)

    return (str:gsub('.', function (c)

        return string.format('%02X', string.byte(c))

    end))

end

but unfortunately after using string.fromhex(str) for data from the serial port I have such error:
bad argument #1 to '?' (number expected, got nil)

and this is raw data from the serial port when I've log it via log(data)
string: O�C��C��

RE: Hex manipulation - Erwin van der Zwart - 18.09.2016

Hi Buuuuudzik,

Try this:

Code:
-- String to HEX

strvalue = 'this is my string'

result = lmcore.strtohex(strvalue)

log(result)

-- HEX to String

hexvalue = '74686973206973206D7920737472696E67'

result = lmcore.hextostr(hexvalue)

log(result)

-- Remove last 2 chars (or checksum)

strvalue = 'this is my string'

result = string.sub(strvalue, 0, (string.len(strvalue) -2))

log(result)

BR,

Erwin

RE: Hex manipulation - buuuudzik - 19.09.2016

(18.09.2016, 21:31)Erwin van der Zwart Wrote: Hi Buuuuudzik,

Try this:

Code:
-- String to HEX strvalue = 'this is my string' result = lmcore.strtohex(strvalue) log(result) -- HEX to String hexvalue = '74686973206973206D7920737472696E67' result = lmcore.hextostr(hexvalue) log(result) -- Remove last 2 chars (or checksum) strvalue = 'this is my string' result = string.sub(strvalue, 0, (string.len(strvalue) -2)) log(result)

BR,

Erwin

Hey Erwin,

thanks for your help but unfortunately it not works probably because I can't use hex in this way:

Code:
hexvalue = '74686973206973206D7920737472696E67'

but only in this way:

Code:
command = string.char(0xBF,0xF4,0xFA,0xB8,0x43,0xFA,0x00,0x00,0x00,0x04,0xA2)

Is there any way to convert such data to string?

RE: Hex manipulation - Erwin van der Zwart - 19.09.2016

Hi Buuuudzik,

command = string.char(0xBF,0xF4,0xFA,0xB8,0x43,0xFA,0x00,0x00,0x00,0x04,0xA2) is the same as command = 'BFF4FAB843FA00000004A2'

Can you show some more you are trying to achieve as this should work ..

BR,

Erwin

RE: Hex manipulation - admin - 19.09.2016

By default hextostr discards zero bytes, you have to pass a second argument for it to keep zeros. Next two lines result in the same binary string:

Code:
c1 = string.char(0xBF,0xF4,0xFA,0xB8,0x43,0xFA,0x00,0x00,0x00,0x04,0xA2)

c2 = lmcore.hextostr('BFF4FAB843FA00000004A2', true)

Your script should probably read:

Code:
result = lmcore.strtohex(data)

log(result)

RE: Hex manipulation - buuuudzik - 19.09.2016

I've tried and this is not the same when I will send to RS485:

Code:
string.char(0x7F,0xF2,0xFA,0xB8,0x43,0xFA,0x00,0x00,0x00,0xFE,0xFD,0x06,0x5B)

and

Code:
'7FF2FAB843FA000000FEFD065B'

Only first way works good second not.

This is my task:
I am preparing:
1) sending commands to somfy rts transmitter without feedback(and it works nice),
2) sending commands to somfy with a feedback message. (to do)

This is a function prepared on this forum:

Code:
function sendSOMFY(command)

  require('serial')

  port = serial.open('/dev/RS485', { baudrate = 4800, parity = 'odd', duplex = 'half', databits = 8, stopbits = 1 })

  port:flush()

  port:write(command)

  port:close()

  sleep(0.1)

end

I must prepare also reading data after sending command GET. But I don't know how many chars will be sended. I've tried this:

Code:
function send_receiveSOMFY(command)

  require('serial')

  port = serial.open('/dev/RS485', { baudrate = 4800, parity = 'odd', duplex = 'half', databits = 8, stopbits = 1 })

  port:flush()

  port:write(command)

  data = port:read(20, 1)

  port:close()

  sleep(0.1)

end

And also in this function is some problem. But this is second thing. When I receive a data from device I must:
1. Delete last 2 bytes which are the checksum.
2. Inverse all bytes.

RE: Hex manipulation - Erwin van der Zwart - 19.09.2016

Hi Buuuudzik,

Here is a script i use for other devices, here is a function to read a line without knowing the lenght, also another HEX function you might want to use:

Code:
---------------------------------------------------------------------

-- *********************** START CONNECTION ********************** --

---------------------------------------------------------------------

-- Load Modules

require('serial')

-- Open connection

port = serial.open('/dev/RS485', { baudrate = 4800, parity = 'odd', duplex = 'half', databits = 8, stopbits = 1 })

---------------------------------------------------------------------

-- *********************** START FUNCTIONS *********************** --

---------------------------------------------------------------------

-- Function to read until carier return is received or timeout

function readline(port, timeout) 

  local char, buf 

  buf = {} 

  while true do 

    char = port:read(1, timeout or 0.2) 

    -- error (timeout) or newline, stop 

    if char == nil or char == '\n' then 

      break 

    -- ignore cr char 

    elseif char ~= '\r' then 

      table.insert(buf, char) 

    end 

  end 

  return table.concat(buf) 

end 

-- Function to write to port and return a reply

function writetoport(port, timeout, command) 

    -- Write data to port as HEX

  port:write(command) 

    -- Call function to read data

  line = readline(port, timeout)

  if #line > 0 then

      return line

  else

    return "No reply received"

  end

end

-- Function to decode hex string value to readable string format

function str2hex(str)

    raw_len = string.len(str)

    i = 1

  while i <= raw_len do

    current_hexvalue = '0x' .. string.format("%02x", string.byte(str, i))

    if value then

      value = value .. ', ' .. current_hexvalue

    else

        value = current_hexvalue

    end

    i = i + 1

  end 

  return value

end

---------------------------------------------------------------------

-- ************************ END FUNCTIONS ************************ --

---------------------------------------------------------------------

---------------------------------------------------------------------

-- *********************** START WRITE/READ ********************** --

---------------------------------------------------------------------

-- Declare command to send to rotel

command = string.char(0xfe, 0x03, 0xa5, 0x10, 0x0a, 0xc2) -- power toggle

-- Send command to port and wait for reply or timeout

reply = writetoport(port, 1, command)-- Timeout is set to 1 second (default = 0.2)

---------------------------------------------------------------------

-- ************************ END WRITE/READ *********************** --

---------------------------------------------------------------------

---------------------------------------------------------------------

-- ************************ START LOGGING ************************ --

---------------------------------------------------------------------

-- Process the reply

if reply == "No reply received" then

  log(reply)

else

  --Decode the reply if hex

  decoded = str2hex(reply)

  log(decoded)

end

---------------------------------------------------------------------

-- ************************* END LOGGING ************************* --

---------------------------------------------------------------------

-- Close port

port:close()

---------------------------------------------------------------------

-- ************************ END CONNECTION *********************** --

---------------------------------------------------------------------

Hope this helps you..

BR,

Erwin

RE: Hex manipulation - admin - 19.09.2016

Of course second one does not work because '7F' == string.char(0x37, 0x46). If you want to send hex string as binary you have to convert it using lmcore.hextostr(str, true) or use string.char.

If by inversion you mean binary XOR, then your function should look like this:

Code:
function convert(str)

  local res, byte

  res = ''

  -- discard last 2 bytes

  for i = 1, #str - 2 do

    -- get single byte

    byte = str:byte(i, i)

    -- invert

    byte = bit.bxor(byte, 0xFF)

    -- add to result

    res = res .. string.char(byte)

  end

  return res

end

RE: Hex manipulation - buuuudzik - 19.09.2016

Thanks a lot for Edwin and Admin.

I have a lot of material Wink

I've checked if the result from hex calculator is the same as from LM and it's perfect Wink