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DonTronics Home Page DT102 RS-485/232 Mini-Terminal.
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2-Jun-1999
Now Available $15AUD for the PCB.

Software Specs:

The DonTronics DT102 PCB has been designed on a 2.5" SimmStick platform, and is same size as the DT205 Relay board.

It has provision for six "Hat Key" type push button switches, and a standard 2 by 16 LCD. The board is designed for the Truly brand LCD, however many others will fit the standard 16 pin header strip provided. Mounting holes are provided for the Truly display which mounts via female/male header pins on the component side of the board, and above components such as the PIC16F84 micro. Yes, the micro will fit in a socket if need be, right under the display. The display is very simply removed.

Two RJ-45 connectors allow RS-485 communications via an 8 wire standard cables. Two jacks means RS-485 can be used on multiple connections or drops. These RJ-45 PCB mount jacks need to be mounted on the solder side of the board.

Also on the solder side of the board, you will find a spot to mount a 5 pin DIN PCB connector, same as the one in your standard PC. This allows an "AT" type keyboard to be plugged in as an alternative to the 6 push button switches.

Other features:
Max-232 and single wire comms will be catered for to some degree. Details to be available in the future.
Configuration jumpers for various programmed feature selections.
On board Piezo buzzer
PIC16F84 4Mhz crystal or resonator operation. (PIC16C61 and others can be used)
LCD contrast control.
Powered from RS-485 bus or SimmBus.
Power ON LED
Debugger LED and link. (RS-485)
Termination resistor and link. (RS-485)
On board +5V regulator and support circuitry.

Special notes regarding the circuitry used.
The keypad matrix uses a technique described on the microchip website. http://www.microchip.com/10/Appnote/Category/12CXXX/Logic/4_012/index.htm

Configuration jumpers ( J4 ) use another multiplexing technique. Essentially when the PIC needs to read the configuration jumpers the i/o port is configured to be an input and the 'E' ( RA2 ) pin is configured to be an output with a logic low. The configuration information is then obtained by reading the appropriate input ports. The resistor pack bias resistors ( RP1 ) for the configuration jumpers are needed to prevent any interaction between the normal functions of the i/o lines and the configuration jumpers.

In 'normal' operation ( when not reading the configuration jumpers )  either the PIC or the LCD would be driving the i/o lines. The bias resistors common line is connected to the 'E' ( RA2 ) line to make sure that the correct
voltage levels are present on the i/o lines during all phases of operation.

Serial communications.
There are three possible hardware interfaces for the serial communications to and from the DT102.
 

  1. RS232

  2. This uses the conventional MAX232 interface chip to provide the appropriate voltage level / conversions. The protocol used is full duplex.
  3. RS485

  4. This uses a LTC485 driver chip to provide the differential drivers and receivers required for RS485. As RS485 is a simplex interface we use RA3 to control the LTC485 driver chip to be in either receive or transmit mode. Because it is only simplex we also multiplex the rx/tx data into the PIC onto RA4. The RS485 interface uses RJ45 connectors to allow multiple devices to be connected to a common serial bus. The RJ45 interface also has power and ground available. By using a serial protocol that has an unique 'identity' each device on the bus can be individually addressed.
  5. Logic interface.

  6. This interface uses the open collector capabilities of the RA4 on the PIC chip. The protocol is also simplex but allows for limited distance communications while only consuming one i/o pin on the PIC. the protocols used are the same as in the RS485 interface.



Software Specs:

At the time of writing, software isn't available to make use of the "AT" keyboard input, however code can be found at Steve Lawther's site at: http://ourworld.compuserve.com/homepages/steve_lawther/keybinfo.htm This may need to be re-configured to suit the DT102 board. Code can also be found at Mauricio Culibrk's site at: http://www.arne.si/~mauricio/PIC.HTM
Steve Lawther's "AT Keyboard/LCD" Schematic

Other Software will be available and full details will be announced in the near future;
Here are some of the specifications:

LCD software specs.
Functionally similar to Peter Andersons http://www.phanderson.com/PIC/ser_lcd_kit.html and/or Ben Wirz http://www.wirz.com/sli-oem/docs/sli-oem.pdf exceptions are the baud rate is limited to two different rates, only one type of display is supported ( should be able to cope with 16, 20 or 40*2 ).

Baud rates either 2400 or 9600, jumper selectable.
Either rs232/rs485/logic, jumper selectable. ( 485 and logic may be in second release )
Addition of 6 way keypad and ability to read from keypad and from LCD.
Will use 'spare' function codes among the 'FE' sequence to access.
Read / Write to EEProm.
Self test mode ( pressing particular keys on reset enters test mode )
Demo test software to run on PC?



All of the documentation for the DT102 board is now on this page.

DonTronics SimmStick and other PCB Prices can be found at:
http://www.dontronics.com/postpcb.html
DonTronics now have dealers in many countries. These dealers can be found at:
http://www.dontronics.com/dealer.html

Board Components:

1 by DT102 PCB

20-Jun-99
Haven't found the time just yet to put together the parts list, however one minor problem has been found with this PCB.
The tracking and signal connections appear to be completely correct.

Diodes D8 and D10 are listed as 1N4004's, but the hole sizes are too small to mount these. You can do many things to overcome this problem. We have found 1N4001's will fit, but these may be awkward to find. You can "Surface Mount" the diodes, or use resistor legs soldered to the board to "T" solder the diodes to. A neat job should be acheivable without too much drama.

Function of D8
Protect the polarity of the PWR input signal, and to "Direction Isolate" the PWR signal to the RJ-45 +12V so that two 12 Volt inputs don't interact. If no power input is used on the RJ-45 bus, then D8 can be a wire link.

Function of D10
Almost the opposite description of D8. J2 pads can be used to short out D10, so that power can be fed from the SimmStick bus to the RJ-45 bus. If power is fed up the RJ-45, then D10 can be shorted out with a wire link.



Subject:         RE: DT102 Issues
   Date:         Mon, 21 Jun 1999 17:29:48 +1000
   From:         "Barry Hay"
     To:         "Don McKenzie" <don@dontronics.com>

OK Don,

Not wanting to dampen any enthusiasm :)

1.  Holes for 1N4004 diodes are too small (at least the diodes I had) D8, D10

2.  Holes for RV1 are too small to take an open frame trimpot, though they would probably fit with a more expensive cermet type trimpot

3.  Holes for J2, J3, J, J6, J9, J10 are too small to take standard square jumper posts.  Also, the spacing between the two posts on each of these jumpers are a than .1" apart, so I had to break apart header strips to fit them in.  Standard shorting jumpers don't fit, so I wire wrapped them.
------------------------
Circuit designer feedback:
All of the jumpers mentioned are what I would consider 'build time' configuration jumpers. I wouldn't expect anyone to need change them after construction, wheras the jumpers that can take the 0.1" header are 'run time' jumpers. YMMV
Rod Egan
Bloke what was responsible in some part for all of this! <grin>
-----------------------
Other than that, I hope to finish the Atmel link tonight.  If I can find a digital camera, I will send a pic.
Regards
Barry Hay



Barry is doing a brain transplant on this one to an Atmel micro.


Subject:              Re: [Fwd: DT102 Issues]
                   Sage Telecommunications <rodegan@

Sage Telecommunications wrote:
>
> Just out of interest did you guys actually get an RJ45 from Jaycar? The
> samples that I sent were from Altronics. I checked the Jaycar catalogue and
> there is no specs for the RJ45 connecters that I can see.
> The Altronics RJ's have the same footprint as Molex, which is pretty much a
> standard footprint.
> And both the right angle and 'straight' RJ45's had the same footprint.
> The odd one out appears to be the Jaycar one!
> Rod

Yes, I did go to Jarcar and get them, I have been assured that the footprint has changed  since I got them. Good old Jaycar!
Don...

(These are Australian companies, however Rod has mentioned that Molex has the same footprint.)

FYI,
The following distributors have RJ45's with the same footprint as the
Altronics samples used for the DT102 PCB layout.

XON / Prospec part number is TS2K88
Farnell part number 257-102
Molex part number 95009-2881
Rod


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