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[on:]

First post, just getting started with arduinos.  Have a 'complex' 4 digit 7 segment display board that I need to have display values that will be calculated from my Mega2560 and don't know if it is an easier approach to try to do this through RS232 port on the display board or try to incorporate serial input.  The board I have is a ETT DSP-4, the documentation is not the greatest on this, but is attached.  Seems to support RS232 485 and serial, but also has MAX chips and decoder/drivers installed.  Anyone ever dealt with these that could offer some advice on methodology?  thanks!

[Reply #1 on:]

It is easy and difficult at the same time.

It looks like a board based on a 8051. It drives 4 hc595s (non-multiplexing). INT0 and T1 (configured as an external interrupt) are used to monitor in the two inputs on DB9 - not sure what protocol it uses - you may want to find a manual for it.

Two approaches:

1) find out what protocol it is and follow it;
2) cut out the 8051 and use your own arduino to drive the hc595s.

[Reply #2 on:]

Much appreciated, as before, the 'manual' is not too explicit on anything, however, it supposes that I can 'simply' put in BCD data on serial in 4 bytes and the onboard MCU will read and display.  Thus, I either need to make the handshake work, or, as you said, cut into the board and jump straight to the decoders using my Arduino to do the MUX and shift reg functions.  I also will be outputting PWM for 12 steps for a graphical representation of digits, and using 2 more of these units as standalone power meter readings, which will also be interesting.  Don't mean to sound ignorant, but I am a fast track newbie and wonder if I can do the BCD outputs or a duplex serial with the Mega for TX RX control serial, not completely sure of the capabilities.  Am VERY looking forward to getting full into the applications that the Arduinos can do, as I have a million uses for them..  I have successfully hand built circuits CMOS and TTL that would have been a breeze had these little buggers been available 10 years ago.  I will contact MFG and see if I can get some other answers, will see how that goes. thx again to all for your input. 10001110101.

[Reply #3 on:]

The manual seems to be for a different board. 8 digit board driven  by MAX7219, vs 4 digit board driven by 89C2051.
If proper documentation is not availalbe, I'd be tempted to wire the Reset pin to be active, and connect a small '328 board (such as Mini-uino, or a Promini) to the '595 control pins and to the RS232 or RS485 IO pins if need that interface.

Promini
http://www.gravitech.us/arpromi5v.html
Duemilanove
http://store.nkcelectronics.com/arduino-duemilanove.html

[Reply #4 on:]

Hi, I'm trying to do the same thing (with an Uno)- any luck?