Modbus, reading registers with strings

[schippi]

Hello,

I'm using  a json profile to read modbus registers from a 4g router.
Reading normal values work perfect but I didn't find a solution how to read out 16 registers and convert it to string format.

A possible solution in LUA is also welcome.

Definition:
   

Thank you  in advance,

Uwe

[Erwin van der Zwart]

Hi Uwe,

Can you try this? I'm not sure how the chars are written in the register so it could not work like this (maybe it's HEX based)

require('luamodbus')
mb = luamodbus.rtu()
mb:open('/dev/RS485', 19200, 'E', 8, 1, 'H')
mb:connect()
mbetslave(1)
r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16 = mb:readregisters(7,16)
result = lmcore.inttostr(r1) .. lmcore.inttostr(r2) .. lmcore.inttostr(r3) .. lmcore.inttostr(r4) .. lmcore.inttostr(r5) .. lmcore.inttostr(r6) .. lmcore.inttostr(r7) .. lmcore.inttostr(r8) .. lmcore.inttostr(r9) .. lmcore.inttostr(r10) .. lmcore.inttostr(r11) .. lmcore.inttostr(r12) .. lmcore.inttostr(r13) .. lmcore.inttostr(r14) .. lmcore.inttostr(r15) .. lmcore.inttostr(r16)
log(result)
mb:close()

BR,

Erwin

[schippi]

Hello Erwin,

many thanks!

I tried your code, but unfortunately I got no result anywhere. "log(result)" serves nothing! It looks like the code stops at the (in homelynk unknown ?) function called "lmcore.inttostr()" ???

Code:

require('luamodbus')
mb = luamodbus.tcp()

mb:open('192.168.2.1', 502)
mb:connect()

r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16 = mb:readregisters(71,16)
log(r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16)

result = lmcore.inttostr(r1) .. lmcore.inttostr(r2) .. lmcore.inttostr(r3) .. lmcore.inttostr(r4) .. lmcore.inttostr(r5) .. lmcore.inttostr(r6) .. lmcore.inttostr(r7) .. lmcore.inttostr(r8) .. lmcore.inttostr(r9) .. lmcore.inttostr(r10) .. lmcore.inttostr(r11) .. lmcore.inttostr(r12) .. lmcore.inttostr(r13) .. lmcore.inttostr(r14) .. lmcore.inttostr(r15) .. lmcore.inttostr(r16)

log(result)
mb:close()

I read out the registers 71 to 87 which should contain the router name: "RUT955" and  logged the variables (r1 to r16) directly and this is the current log

Code:

RouterModbus 21.02.2018 20:07:10
* arg: 1
 * number: 21077
* arg: 2
 * number: 21561
* arg: 3
 * number: 13621
* arg: 4
 * number: 18487
* arg: 5
 * number: 22064
* arg: 6
 * number: 12848
* arg: 7
 * number: 0
* arg: 8
 * number: 0
* arg: 9
 * number: 0
* arg: 10
 * number: 0
* arg: 11
 * number: 0
* arg: 12
 * number: 0
* arg: 13
 * number: 0
* arg: 14
 * number: 0
* arg: 15
 * number: 0
* arg: 16
 * number: 0

I attached the routers short modbus manual.

B.R,

Uwe

[Erwin van der Zwart]

Hi Uwe,

Thanks for the values, now i could figure out that each register holds 2 chars.

Try this (:

PS: Result is RUT955H7V020

Code:

require('luamodbus')
mb = luamodbus.tcp()

mb:open('192.168.2.1', 502)
mb:connect()

r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16 = mb:readregisters(71,16)

function twobytetochars(value)
 charsvalue = lmcore.hextostr(lmcore.inttohex(value,2))
 return charsvalue
end

if r1 then r1 = twobytetochars(r1) else r1 = "" end
if r2 then r2 = twobytetochars(r2) else r2 = "" end
if r3 then r3 = twobytetochars(r3) else r3 = "" end
if r4 then r4 = twobytetochars(r4) else r4 = "" end
if r5 then r5 = twobytetochars(r5) else r5 = "" end
if r6 then r6 = twobytetochars(r6) else r6 = "" end
if r7 then r7 = twobytetochars(r7) else r7 = "" end
if r8 then r8 = twobytetochars(r8) else r8 = "" end
if r9 then r9 = twobytetochars(r9) else r9 = "" end
if r10 then r10 = twobytetochars(r10) else r10 = "" end
if r11 then r11 = twobytetochars(r11) else r11 = "" end
if r12 then r12 = twobytetochars(r12) else r12 = "" end
if r13 then r13 = twobytetochars(r13) else r13 = "" end
if r14 then r14 = twobytetochars(r14) else r14 = "" end
if r15 then r15 = twobytetochars(r15) else r15 = "" end
if r16 then r16 = twobytetochars(r16) else r16 = "" end

result = r1 .. r2 .. r3 .. r4 .. r5 .. r6 .. r7 .. r8 .. r9 .. r10 .. r11 .. r12 .. r13 .. r14 .. r15 .. r16
log(result)

mb:close()

BR,

Erwin

[admin]

More universal solution:

Code:

require('luamodbus')
mb = luamodbus.tcp()

mb:open('192.168.2.1', 502)
mb:connect()

function readstring(mb, address, length)
  local data = { mb:readregisters(address, length) }
  local bytes = {}

  for _, reg in ipairs(data) do
    if type(reg) == 'number' then
      -- high 8 bits
      local b1 = bit.band(bit.rshift(reg, 8), 0xFF)
      if b1 > 0 then
        bytes[ #bytes + 1 ] = b1
      end

      -- low 8 bits
      local b2 = bit.band(reg, 0xFF)
      if b2 > 0 then
        bytes[ #bytes + 1 ] = b2
      end
    end
  end

  -- convert table of byte values to string
  return string.char(unpack(bytes))
end

result = readstring(mb, 71, 16)
log(result)

mb:close()

[schippi]

Hello Erwin,

the result is:

RouterModbus2 22.02.2018 11:46:00
* string: RUT955H7V02043

Your solution works perfect and i prefer the second one, caused on it's flexibility!  

I'll give you a very big "THANK YOU" for your enthusiastic service

Have a nice day and b. r.,

Uwe

PS.: I know, that the success of this product depends essentially on such colleagues as you.