actually, just got email from company that made the product. although reply was incomplete, at least it was step in the right direction.
I am posting this for any desperate souls out there who might be looking for some clue on how to get this unit to respond (also should apply to similar products like ET-DSP6 and ET-DSP8).
first of all there is some basic code in it already and at least confirmed that RS232 port works. Port settings are 9600, 8-N-1.
also, as is, there is no reply from the unit on RS232, digital I/O etc are not programmed either (this was meant as 'open platform') for RS422/485 option to work nodes need to be addressable.
the only way to see any response from unit is to connect it properly, set correct baud rate and send valid command.
commands are (exactly) 15 characters followed by CRLF such as:
'*01:06123456789' <CRLF> (this displays '1234' on 4-digit display, excess characters are not displayed but must be sent)
'*' is header
'01' is node address (unless program is changed by user, it is always '01')
':06' is actual command (the only command in this case)
'12346579' is data where valid characters are '0'-'9', 'A'-'F','.'
other characters are not displayed but can be used as space holder (didn't work with all characters, but 'g' for example was fine).
proper wiring (only for 4-pin connector marked RS232):
the connector pins are not marked, but the pin1 has square solder pad.
when MAX/OPTO jumper is in OPTO position:
- connect Tx from PC serial port to pin1
- connect GND from PC serial port to pin2.
when MAX/OPTO jumper is in MAX position:
- connect Rx from PC serial port to pin3
- connect Tx from PC serial port to pin2
- connect GND from PC serial port to pin4.
I will have to get to this and modify code (time permitting, now this is on back burner). The most needed change for RS485 support is node addressing. I would like to use available IO for this. For out of box product this means inserting divers 75176 and serial eprom. Eprom must contain ID value.
When unit is powered from 12V, consumption was 2-50mA (2mA when display is off and 50mA when every segment and every dot was on).
4 digital I/O are on DB9 connector so up to 16 nodes can be selected using just plugs with hardwired binary address.
I'll probably also swap the MCU for LS version so programming using low voltage is possible.
@Norlin:
Thank you for reply. I like the Keil's products but they won't fit my budget. I'll either use the Atmel's software or SDCC.