Decoding serial input

DiverBob · 2014-06-08 18:04

It's getting late and my mind has decided it doesn't want to play anymore! A search through the forum didn't help so I'll ask here.

I want to output a series of numbers using the Parallax Serial Terminal object. The series will consist of a "T" for a start indication, a comma, a number, comma, and another number ("T",n,nnn). I can type the series into the serial terminal but my attempts at decoding it in the prop are falling flat. Any similar examples available out there?

Thanks

Peter Jakacki · 2014-06-08 18:29

DiverBob wrote: »

It's getting late and my mind has decided it doesn't want to play anymore! A search through the forum didn't help so I'll ask here.

I want to output a series of numbers using the Parallax Serial Terminal object. The series will consist of a "T" for a start indication, a comma, a number, comma, and another number ("T",n,nnn). I can type the series into the serial terminal but my attempts at decoding it in the prop are falling flat. Any similar examples available out there?

Thanks

Well that's straightforward in Forth but you can do something similar in Spin by simply sitting in a loop which tests for digits and shifts them into an accumulator ( acc := (acc*10) + (char-$30). So when you encounter a non-digit you simply terminate with the result as the number. So this will work with commas or end-of-line but the T should be passed in a variable so that the app knows to disregard the result and synch or whatever. Not quite sure why you need to say "T" with the quotes though, it seems very redundant. Personally I would just use a symbol like a colon immediately followed by the first number :n,nnn

Phil Pilgrim (PhiPi) · 2014-06-08 19:00

DiverBob,

I'm a bit confused by your post. You say you want to output (from the Prop) data in the given format, but the title and subsequent comments seem to indicate an input (to the Prop) operation. Which is it?

-Phil

DiverBob · 2014-06-09 03:19

Phil Pilgrim (PhiPi) wrote: »

DiverBob,

I'm a bit confused by your post. You say you want to output (from the Prop) data in the given format, but the title and subsequent comments seem to indicate an input (to the Prop) operation. Which is it?

-Phil

I told you my mind wasn't with it last night! What I meant was that I want to use the Parallax Serial Terminal object on the prop to recieve data from my computer. I want to input a command string such as T,1,90 followed by a return char. The commas are to delineate the individual values following the start character. That command string then needs to be interpreted by the prop. Eventually instead of me typing in the command string, another prop will be providing the input to the prop.

Last night I couldn't figure out how to parse the input string into its different components. This morning I'm doing better and have a couple of ideas to test tonight but as long as I've asked the question it would be nice to see how others have solved this type of issue. Oh yes, the T is just a transmit character to indicate the start of the command sequence, I just typed quotes around it, seemed like a good idea at the time...

max72 · 2014-06-09 06:26

It' very similar to a NEMA string like the ones coming from a GPS, and there are many objects around.
That would be my starting point..

Massimo

Dave Hein · 2014-06-09 08:39

In C you can do something like this:

#include <stdio.h>

char buffer[100];

int main(void)
{
    int int1, int2;
    while (gets(buffer))
    {
        if (sscanf(buffer, "T,%d,%d", &int1, &int2) == 2)
            printf("int1 = %d, int2 = %d\n", int1, int2);
    }
    return 0;
}

I've tested this with GCC under Cygwin, and it correctly decodes a string with the format "T,#,#". It rejects any string that does not follow that exact format. I haven't tested this under PropGCC so I don't know if it works exactly the same.

EDIT: I tested it with PropGCC, and it works correctly on the Prop also.

JonnyMac · 2014-06-09 09:20

Do a forums search on "parser" -- there are a few examples in Spin that I've participated in.

DiverBob · 2014-06-11 18:48

Thanks for all the help so far! I think I found the answer I've been looking for in an object written by Phil Pilgrim called regex, a regular expression parser that it appears he wrote for GPS decoding. I've modified his demo and I can get it to work when I specify the input string in the program but I can't enter the same string in the Parallax Serial Terminal and get an output. I believe the problem is the getstr command used to input the string from the terminal to the prop but I can't figure out what other choice to use that works in FullDuplexSerialPlus. I've been using the Parallax Serial Terminal object for all my terminal work, first time I've used this object for serial communications.

Maybe someone else can see where I went wrong:The program as it stands works until I add in the commented out lines and then comment out the line teststr := string("$T,1,2,345")

con

  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000

  CLK_FREQ = ((_clkmode - xtal1) >> 6) * _xinfreq
  MS_001   = CLK_FREQ / 1_000
  
con

  RX1 = 31
  TX1 = 30
  SDA = 29
  SCL = 28

  CS  =  27
  CLK =  26
  DIO =  9

obj
  io            : "FullDuplexSerialPlus"
  re            : "regex"

pub main
  Serialtest

pub SerialTest | teststr, pattern, resaddr, rslt, i  
'test inputing data from PST and echoing it back to the PST
' input string format: "$T,1,2,345"
  io.start(31, 30, 0, 9600)
  io.tx(16)
'  repeat
'    pauseMSec(1000)
'    io.Str(String(pst#NL, "Enter command: "))
'    io.getstr(teststr)
    teststr := string("$T,1,2,345")
    pattern := string("\$T\s*,($1[\d])\s*,($2[\d])\s*,($3[\d]+)\s*")
     
    io.str(string("String:", 13, 13))
    io.str(teststr)
    io.str(string(13, 13, "Pattern:", 13, 13))
    io.str(pattern)
     
    rslt := -cnt
    resaddr := re.match(teststr, pattern, re#NOALT)
    rslt += cnt
     
    io.str(string(13, 13, "Time: "))
    io.dec(rslt / 80_000)
    io.str(string(" ms."))
    io.str(string(13, 13, "Results:", 13))
     
    if (resaddr < 0)
      io.tx(13)
      io.str(string("Error #"))
      io.dec(-resaddr)
    elseif (resaddr == 0)
      io.tx(13)
      io.str(string("No match."))
    else
      repeat i from 0 to 9
        if (rslt := long[resaddr][i])
          io.tx(13)
          io.dec(i)
          io.str(string(": "))
          io.str(re.field(i))
     
      io.str(string(13, 13, "Remainder of string:", 13, 13))
      io.str(re.remainder)

PUB pauseMSec(Duration)
'' Pause execution in milliseconds.
'' Duration = number of milliseconds to delay
  waitcnt(((clkfreq / 1_000 * Duration - 3932) #> 381) + cnt)

SerialParsingTest - Archive [Date 2014.06.11 Time 21.34].zip

kuroneko · 2014-06-11 19:05

The getstr method expects an address to a byte array (where a string can be stored), e.g. (untested)

VAR
  [COLOR="#FF0000"]byte  buffer[128][/COLOR]

PUB SerialTest | teststr, pattern, resaddr, rslt, i  
'test inputing data from PST and echoing it back to the PST
' input string format: "$T,1,2,345"
  io.start(31, 30, 0, 9600)
  io.tx(16)
  repeat
    pauseMSec(1000)
    io.Str(String(pst#NL, "Enter command: "))
    io.getstr(teststr[COLOR="#FF0000"] := @buffer{0}[/COLOR])
    pattern := string("\$T\s*,($1[\d])\s*,($2[\d])\s*,($3[\d]+)\s*")
  ...

Currently you'd pass a random stack value (uninitialised local variable).

rogersyd · 2014-06-12 17:30

DiverBob wrote: »

Any similar examples available out there?

Thanks

Check out this book and the associated code:
http://www.parallax.com/product/32316
ftp://ftp.propeller-chip.com/

There is a terminal project included there that contains some great token parser routine. Even without the book the code should be useful to you as it is well commented.

DiverBob · 2014-06-13 13:34

kuroneko wrote: »

The getstr method expects an address to a byte array (where a string can be stored), e.g. (untested)

VAR
  [COLOR="#FF0000"]byte  buffer[128][/COLOR]

PUB SerialTest | teststr, pattern, resaddr, rslt, i  
'test inputing data from PST and echoing it back to the PST
' input string format: "$T,1,2,345"
  io.start(31, 30, 0, 9600)
  io.tx(16)
  repeat
    pauseMSec(1000)
    io.Str(String(pst#NL, "Enter command: "))
    io.getstr(teststr[COLOR="#FF0000"] := @buffer{0}[/COLOR])
    pattern := string("\$T\s*,($1[\d])\s*,($2[\d])\s*,($3[\d]+)\s*")
  ...

Currently you'd pass a random stack value (uninitialised local variable).

That worked! I went back and looked at the getstr() command in FullDuplex SerialPlus, don't know why I missed seeing that it needed a string pointer...

Thanks for the help. Now to get back to work on using the information!

DiverBob · 2014-06-14 12:17

Although the input string is being broken up correctly, I don't seem to be able to assign the values to another variable. I think I'm missing something basic here but after 3 hours of playing with it, I'm fresh out of ideas. Here is the code in question:

con

  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000

  CLK_FREQ = ((_clkmode - xtal1) >> 6) * _xinfreq
  MS_001   = CLK_FREQ / 1_000
  
con

  RX1 = 31
  TX1 = 30
  SDA = 29
  SCL = 28

  CS  =  27
  CLK =  26
  DIO =  9

var
  byte buffer[128]
  word leg, command, parameter

obj
  io            : "FullDuplexSerialPlus"
  re            : "regex"

pub main
  Serialtest

pub SerialTest | teststr, pattern, resaddr, rslt, i  
'test inputing data from PST and echoing it back to the PST
' input string format: "$T,1,2,345"
  io.start(31, 30, 0, 9600)
  io.tx(13)
  repeat
    pauseMSec(1000)
    io.Str(String("Enter command: "))
    io.getstr(teststr := @buffer{0})
'    teststr := string("$,1,2,345")
    pattern := string("\$\s*,($1[\d])\s*,($2[\d])\s*,($3[\d]+)\s*")
     
    rslt := -cnt
    resaddr := re.match(teststr, pattern, re#NOALT)
    rslt += cnt
     
    if (resaddr < 0)
      io.tx(13)
      io.str(string("Error #"))
      io.dec(-resaddr)
    elseif (resaddr == 0)
      io.tx(13)
      io.str(string("No match."))
    else
      repeat i from 0 to 3
        if (rslt := long[resaddr][i])
          io.tx(13)
          io.dec(i)
          io.str(string(": "))
          io.str(re.field(i))
          case i
            1: leg                := re.field(i)
            2: command            := re.field(i)
            3: parameter          := re.field(i)
    io.tx(13)
    io.str(string("Leg: "))
    io.dec(leg)
    io.tx(13)
    io.str(string("Command: "))
    io.dec(command)
    io.tx(13)
    io.str(string("Parameter: "))
    io.dec(parameter)
    io.tx(13)
    io.tx(13)
    
     
PUB pauseMSec(Duration)
'' Pause execution in milliseconds.
'' Duration = number of milliseconds to delay
  waitcnt(((clkfreq / 1_000 * Duration - 3932) #> 381) + cnt)

The problem is when I attempt to assign the values to the Leg, command, and parameter variables. Here is the output I'm getting when entering a string of $,1,2,345 in to the program:

Enter command:
0: $,1,2,345

1: 1
2: 2
3: 345
Leg: 3246
Command: 3246
Parameter: 3246

Hopefully someone will see what mistake I'm making here.

SerialParsingTest - Archive [Date 2014.06.14 Time 15.01].zip

John Abshier · 2014-06-14 15:39

I don't have the re object to look at but I am guessing that re.field returns a string pointer which works fine in the io.str(re.field(i)). Later you assign the string pointer to a long in the case statement. What you want to do is to convert the string pointed to by re.field to a long (an integer).

John Abshier

DiverBob · 2014-06-14 18:20

John Abshier wrote: »

I don't have the re object to look at but I am guessing that re.field returns a string pointer which works fine in the io.str(re.field(i)). Later you assign the string pointer to a long in the case statement. What you want to do is to convert the string pointed to by re.field to a long (an integer).

John Abshier

I archived the project in my last post, that has the re object object in it. I believe the output of re.field is a string and the variables are all bytes. You should be able to open the archive and run the code, it contains everything needed. I believe I've tried what you are talking about but didn't get a usable output. It appears that the output is stored in the resaddr array but I couldn't get a usable output there either.

John Abshier · 2014-06-14 19:28

I am traveling, but will try to look at it later next week if no one else answers. For some reason I cannot download a zip file from the forum on my laptop. It wants to do something with attachment.php.

John Abshier

Bill Henning · 2014-06-14 20:32

Bob,

See http://forums.parallax.com/showthread.php/122295-Converting-string-to-decimal?p=905112&viewfull=1#post905112

That should do it for you

You can find other relevant/useful links with the following google search:

https://www.google.ca/#q=string+to+integer+in+spin+for+propeller

Hope that helps!

Bill

DiverBob · 2014-06-15 07:58

Bill Henning wrote: »

Bob,

See http://forums.parallax.com/showthread.php/122295-Converting-string-to-decimal?p=905112&viewfull=1#post905112

That should do it for you

You can find other relevant/useful links with the following google search:

https://www.google.ca/#q=string+to+integer+in+spin+for+propeller

Hope that helps!

Bill

That was the ticket! The Str2Dec routine is what I needed to convert the output correctly. Thanks for the help, now on to testing that input sequence to see if it will move the robot leg correctly.

Bill Henning · 2014-06-15 15:09

You are welcome - glad to help

DiverBob wrote: »

That was the ticket! The Str2Dec routine is what I needed to convert the output correctly. Thanks for the help, now on to testing that input sequence to see if it will move the robot leg correctly.

msrobots · 2014-06-15 17:10

John Abshier wrote: »

I am traveling, but will try to look at it later next week if no one else answers. For some reason I cannot download a zip file from the forum on my laptop. It wants to do something with attachment.php.

John Abshier

Some Forum glitch. You need to replace attachment.php by the correct filename to save.

It is doing this for a while now. Filename always shows as attachment.php.

Enjoy!

Mike

Tracy Allen · 2014-06-15 20:58

You're bringing in heavy artillery for this relatively simple problem. Just for fun, here is a simple parser. It just waits for the "$," combination, and then expects three numbers separated by a non-digit, and terminated by a non-digit. For example, "1,2,345 <cr>"

[SIZE=1][FONT=courier new]CON
  _clkmode = xtal1 + pll16x                '
  _xinfreq = 5_000_000

  N_VALUES = 3
  LAST_INDEX = N_VALUES - 1

VAR
  long idx, value[N_VALUES]

OBJ
  fds : "fullDuplexSerial"

PUB trial | char
  fds.start(31,30,0,9600)
  waitcnt(clkfreq/10+cnt)

  repeat   ' for each string entered
    repeat idx from 0 to LAST_INDEX   ' clear data array
      value[idx]~
    idx~                           ' zero array index
    fds.str(string(13,13,"waiting for data... "))
    repeat until fds.rx == "$"     ' expect a "$"
    if fds.rx <> ","           ' expect "," else restart
      next
    repeat             ' capture digits of each number
      repeat while (char := fds.rx) => $30 and char =<$39
        value[idx] := value[idx] * 10 + char - $30
    until idx++ == LAST_INDEX   


    fds.str(string(13,"the values are: "))              ' show what we got.
    repeat idx from 0 to LAST_INDEX
      fds.tx(13)
      fds.dec(idx)
      fds.tx(":")
      fds.dec(value[idx])
[/FONT][/SIZE]

DiverBob · 2014-06-16 06:23

Great routine! I know the parser I used was over kill but half the fun is the journey, right! I like the simplicity of your routine, I'll try it out later and see how it goes.
That's the best thing about here, all the different ways to go about accomplishing the same goal. I learned a lot through this exercise and that was at least half the fun!

Decoding serial input

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