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A Modbus-slave for a handwheel (Propeller) — Parallax Forums

A Modbus-slave for a handwheel (Propeller)

Nick MuellerNick Mueller Posts: 815
edited 2010-11-23 05:46 in Robotics
Hi!

I have built this Modbus-interface (slave) to go to my mill (MAHO 700C). It will handle all the signals (switches, pushbuttons) in a remote-control (a hand wheel for jogging etc.).

Let's start with pictures:
if0.JPG

The un-populated PCB (etched by PCB-pool, layout with EAGLE).

if1.JPG

Soldering side of PCB. Yes, I made an error in the schematics. Flipped TXD and RXD.


TBC ...
800 x 568 - 207K
800 x 533 - 138K
if0.JPG 207.4K
if1.JPG 138.1K

Comments

  • Nick MuellerNick Mueller Posts: 815
    edited 2010-11-23 05:35
    if3.JPG

    Board populated.

    if4.JPG

    LCD showing some message.


    TBC...
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    if3.JPG 133.1K
    if4.JPG 140.7K
  • Nick MuellerNick Mueller Posts: 815
    edited 2010-11-23 05:37
    if6a.jpg

    Connections to the outside.

    if5.JPG

    Also needed an RS232 to RS485 converter. I'm already awaiting the first time I connect a DSub-9 the right way. :D

    TBC...
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    if5.JPG 124.4K
    if6a.jpg 133.9K
  • Nick MuellerNick Mueller Posts: 815
    edited 2010-11-23 05:46
    if7.JPG

    And here part of the control. Not showing the Modbus-interface.

    Technical data:
    * 24 TTL outputs. Enough to drive a LED
    * 24 TTL inputs (with pull downs).
    * In and out is done with shift registers. 3 * 74595 & 3 * 74166
    * opto-isolated RS232 (with an MAX232). Does up to 115200 Bd.
    * isolated two-wire (half duplex) RS485 with an ADM2483, also up to 115200 Bd.
    * bus (4-bit) to the LCD (a EA DIP204B).
    A few jumpers and LEDs for configuration and signaling.

    Code is written with ImageCraft's C-compiler.
    Response time (from last bit received 'till first bit sent) is 640 µs.
    The LCD is written to over Modbus by writing to 40 assigned registers (a Modbus-register has 16 bit). A complete screen update takes 2 ms at the control.
    The software on the Prop also has a configuration menue (by connecting a terminal to the RS232 and setting a jumper). Base-addresses for coils, inputs and LCD can be set. Also baudrate, ASCII- or RTU-mode, response-delay, end-of-message-time-out for RTU and other things I forgot. :-)


    Nick
    800 x 600 - 215K
    if7.JPG 215.3K
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