I just picked up two Futaba 20x2 VFD. On the back, under the name is the model number "NA202MD08BC". Also silkscreened on the edge is "202MD8BF". I have done extensive Googling and don't find anything on this model.
The display is part of a POS customer display. A daughter board plugs into the VFD. The daughter board takes input from what appears to be a standard parallel printer port. The parallel data is a pass-through with one cable in and one cable out. On the daughter board is a Winbond W78C32B uC, a 93c06 serial EEPROM, a 6264 SRAM, an EPROM, a DS1232 Micromonitor and a few TTL chips.
The VFD has a 20-pin connector. Tracing back from this connector to the other components, I get the following connections:
There are only two chips on the back of the VFD. Both are OKI C1162 drivers. I don't know if there is any on-glass circuitry. Of course, the high voltage circuitry is also on the back of the VFD.
I would like to use the bare VFD without the daughter board. Is there a library to use this display with an arduino?
If I am understanding things correctly, the above library has to handle clocking in the raw data to the OKI drivers. It seems that this VFD may not have any onboard smarts.
It is late, so I'll hook things up tomorrow to try the library. If anyone has any insight in the mean time, please post.
There are only two chips on the back of the VFD. Both are OKI C1162 drivers. I don't know if there is any on-glass circuitry. Of course, the high voltage circuitry is also on the back of the VFD.
Well it seems you have identified the serial comm signal, power & ground, but the question is can you separate the
VFD from the daughter board and if you could how would you set the baud rate ?
If I understand you correctly you want to replace the existing uC with an Arduino, and dispense with the EEPROM , SRAM, & EPROM and the DS1232.
Did you read the datasheets for the 78c32B or DS1232 (attached).?
It seems like all the pinout info you would need is contained in the pinout for the 78c32B.
Is there a dipswitch that might be the baudrate select or do you think there is some default speed ?
Have you attempted to draw a proposed wiring schematic for your target system based on the info available from the
datasheets for the ic's. How close are you to actually wiring it up and testing it ?
Thanks to those who posted datasheets. I did already have those. The one thing that is different about this display, compared to all the others that I have seen online, is that this one only has the two OKI drivers. There is no other chip to provide any smarts. There are no jumpers or switches for setting baudrate.
The closest match that I have seen is the Prime VFD that is 20x4. That one has an additional chip, however. I suspect that like the Prime VFD, this one will require clocking in the raster data continuously.
The daughterboard is removable from the display. The POS pole assembly is model PD1100TP from Ultimate Technologies. All I found is a simple specsheet that tells me that the assembly is a parallel pass-through (TP) and it takes 9 VDC @ 900 mA.
I did power it up and it displays a sign-on message. The daughter board has two pushbutton switches that let you set some options. It apparently understands at least three POS protocols.
I could use the display with the daughterboard, but there are two drawbacks to that. First, the combination is much larger than just the VFD. Second, the interface is parallel and requires too many pins to suit me.
I recently bought a Bus Pirate, but haven't used it yet. I guess this will be a good opportunity to learn how. I'll see if I can monitor the serial communications between the daughter board and the display. Then I'll have to see if I can make sense of it This type of reverse engineering is new to me.
So why can't you remove the daughter bd and connect your Arduino Tx & Rx , gnd & +5V to display pins
1,3,5, & 13 and connect your RESET to pin -11 ?
Maybe one of the standard baudrates will work.
You said it was parallel but your pin info shows serial pins .
Did I misunderstand what you were trying to convey ?
The daughterboard takes in parallel data. The VFD has some type of serial interface. As I mentioned earlier, I don't think it is a smart display that will understand standard serial-type protocols (RS232, SPI). I believe that it needs to be constantly refreshed with raster data from a microcontroller.
I should know more shortly. I just came back from grocery shopping, so had to put the hacking on hold.
If it is a serial display I find that hard to believe. All these VFD displays , especially the older ones, used some
kind of standardization. I had one that all you needed to know was correct pins and the default baudrate
and from that point on you were good to go. The only criteria is that you are sending ASCII. Anything ASCII
will be displayed. As far as addressing line 2 , I don't know. I never said anything about RS232. All these
displays are going to use TTL level signals and ASCII.
I did some data captures with the Bus Pirate. I was monitoring all five signals between the daughterboard and the display. Since the Bus Pirate captures so few samples, I had to power things up and then hit "capture" in the OLS client. I tried to use triggers, but for some reason, the capture started before power was applied, every time.
On powerup, the daughterboard sends commands to display a welcome message, consisting of the company name and a copyright. Of course, what I capture depends on when I hit the "capture" button during this powerup sequence.
I did try several different methods of talking to the display. None of them worked.
Being that the Bus Pirate is so limited as a logic analyzer, I think I'll buy one of those 8-channel USB devices off ebay. They supposedly can capture for long periods of time. That way, I should be able to capture everything from a cold start. Then, perhaps I can make sense of things.
While I was obviously hoping to find a way to communicate with them right away, I'll just set them aside until I get that logic analyzer.
I took a chance buying them, as they were part of a POS system. I got the plastic housing, the pole and cables. I knew that there would be some type of VFD inside, but didn't know what I would find until I took one apart. I got them cheap, so it isn't a big loss, even if I never figure these out.
They are very nice displays, though. They are still very bright and un-burned. The digits are huge (10.5 mm tall). Hopefully, I'll get them working some day.
I had earlier pinned-out the display connector to the daughterboard, trying to get an idea of what type of serial interface this VFD had. Well, I just pinned-out the VFD driver chips (OKI MSC1162A) to the 20-pin connector.
CLK = clock
DIN = data in
/CL = clear (blank) display
LS = latch strobe
The OKI drivers are essentially large 40-bit shift registers that output high voltage to drive the rows and columns of the VFD 5x7 segments.
This seems to confirm that this display has to be driven in a raster format and has no internal fonts, similar to that Prime VFD that already has an arduino library. Obviously, there are differences, as I tried the Prime VFD library and got no display.
When I have more time to fool with this, I'll see if I can wrap my head around the datasheets and see if I can figure out how to drive these. Being an Arduino newbie, I'm not sure if I can come up with anything or not.
The VFD I used for Junior Class Project must have had a ROM with all the ASCII characters in it because it
pretty much plug and play. I just sent TTL serial ASCII and it worked. I think there were control codes for
some things but I remember being a 1-line display instead of 2. I should have take a picture of it but in
1992 the cell phone camera resolution was terrible. I don't even remember if mine had one.
This type of reverse engineering is new to me.