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Send a frame of ascii data using a BS2. — Parallax Forums

Send a frame of ascii data using a BS2.

forbesgforbesg Posts: 6
edited 2011-05-30 21:15 in BASIC Stamp
I need to simulate an instrument that sends data in a frame that is 10 bytes. The data is ASCII. This data must be sent to an RS232 port on, say pins 0 and 1. The baud rate will be 2400, data bits will be 8, no parity
Example frame will look like the following.
sExample 1 Displaying data of a scale:-10 Code of exclusive or check: 0C
Example 2 Displaying data of a scale:22040 Code of exclusive or check:14
Start
Weighing data(including subtraction sign and decimal point)
Exclusive or check
End
Low




High
Low
High
02
30
34
30
32
32
20
34
31
03

Comments

  • stamptrolstamptrol Posts: 1,731
    edited 2011-05-27 07:22
    Is this to simulate a particualr manufacturer's scale? I've used the Stamp to simulate Toledo, Rice Lake, Weightronics indicators without too much trouble.

    You'll use serout and assemble the string you need. You'll have to have a loop to calculate the checksum according to the directions given by the manufacturer.

    Note that using pins 0 or 1 will require the INVERTED form of SEROUT in order to give the receiving device a signal aproximating the rs-232 levels. Don't be surprised if you have to add a MAX232, MAX233 or ST232 chip to give an on-spec rs-232 set of voltages.

    I've attached an old version of a string generator which generates a few specific strings. Note that it didn't need the checksum.

    Cheers,


    forbesg wrote: »
    I need to simulate an instrument that sends data in a frame that is 10 bytes. The data is ASCII. This data must be sent to an RS232 port on, say pins 0 and 1. The baud rate will be 2400, data bits will be 8, no parity
    Example frame will look like the following.
    sExample 1 Displaying data of a scale:-10 Code of exclusive or check: 0C
    Example 2 Displaying data of a scale:22040 Code of exclusive or check:14
    Start
    Weighing data(including subtraction sign and decimal point)
    Exclusive or check
    End
    Low




    High
    Low
    High
    02
    30
    34
    30
    32
    32
    20
    34
    31
    03
    bs2
    bs2
    scaltrol_test.bs2
    3K
  • forbesgforbesg Posts: 6
    edited 2011-05-28 07:58
    Hi Tom,

    Thanks for this info. I am attaching sample data frames I will need to send. This is a wireless bluetooth application, so I will be sending the data to a BT to serial converter attached to my laptop. In actual use, the scale will send the data to this serial converter. So I will need to attach the serial cable to the BS2. I already have a backpack serial LCD on pin 0, I believe. All the other pins are available. So I guess I will need the x232 chip you mentioned. It has been years since I have done anything serious with a BS2, so please forgive my ignorance here.
    Thanks for the help.

    Dan
    doc
    doc
    Example data frames.doc
    28K
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-05-28 08:09
    forbesg,
    Are you using a Board of Education (BoE)?
  • stamptrolstamptrol Posts: 1,731
    edited 2011-05-29 05:03
    Looks like a pretty typical scale string. Note that the data bytes are arranged from low to high order, so it may be necessary to flip them.

    Using your first example, the Stamp would send: (I just converted each 2-character hex code to ASCII. From left to right, that gives: STX, 0, 1, -,spc,spc,spc,chksum,chksum,ETX)

    SEROUT 8,com_ind,[002,048,049,045,032,032,032,067,048,003]

    The serial side of the BT converter should be able to connect to the programming port on the Stamp. That would eliminate the need for the xx232 chip.

    You'll also have to create a routine to calculate the checksum characters, but only if they're needed by the receiving system.

    Cheers,
  • forbesgforbesg Posts: 6
    edited 2011-05-30 08:16
    Tom,

    Thanks. I just need to demonstrate that the system works. I tried to connect the BT serial port to the BS2 and connect using the stamp editor. It reports "No stamp connected" or something similar. It is an IO Gear GBS301. Perhaps I need to adjust some of its timing settings.
    It has been years since I have looked at using my stamps. This is a re-learning process for me. Something I hope to use to launch a new side to my laser business. Thanks again for your help. Enjoy the holiday and be safe.

    Forbes
  • forbesgforbesg Posts: 6
    edited 2011-05-30 08:22
    Hello PJ,

    I am using an OLD BS2 board with an OLD BackPack LCD display. Old as in 12 years or so.
    ForbesG
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-05-30 09:58
    forbesg,
    I want to avoid clouding the issue at hand. Just wanted to know if your board was a Parallax product or your own devise. If it's a Parallax product then it should have the 9_pin programming port. Given that, you can/could send your test frames using SEROUT 16... and thereby pin#2 of the 9_pin.

    Get the latest PBASIC IDE.

    If you make your own 9_pin cable using just pin#2 and pin#5 then you don't have to worry about "echo" and all that stuff (from the on-board 4k7 resistor between pin#2 and pin#3).
  • stamptrolstamptrol Posts: 1,731
    edited 2011-05-30 12:16
    You may not be able to use BT to program the Stamp. However, the serial data should work fine.

    Tom
  • forbesgforbesg Posts: 6
    edited 2011-05-30 21:14
    PJ,

    Thanks. I have the latest PBasic download from Parallax so I should be fine there. I plan on making a simple program that transmits the serial data on one of several button pushes, thus simulating an on demand scale output. Once I have the program running, I should be able to remove the programming cable and plug in the BT cable. Thanks for the additional info.

    ForbesG
  • forbesgforbesg Posts: 6
    edited 2011-05-30 21:15
    Tom,

    Exactly, please see my reply to PJ. You both have advance my knowledge greatly.
    I will modify and use your program.
    Thanks,

    Forbesg
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