And this helps a lot: https://en.wikipedia.org/wiki/Intel_8255
On Wednesday, June 5, 2019 at 11:53:39 AM UTC-4, Keith Moore wrote: > > Yup. And... I am probably wrong about the parallel interface. John > describes it well. I was a comm jock once a long time ago before these were > made. But I don't remember my line-level stuff. It would be normal for it > to be parallel in an internal design like this because it is faster to > drive these. But it does look like a load and latch interface to two > logical busses. > > On Wednesday, June 5, 2019 at 11:19:21 AM UTC-4, GastonP wrote: >> >> Most Arduino kits but the smallest ones (i.e.: Mini) and Raspberry Pi >> have enough GPIO pins available to do it without need to resort to serial >> to parallel. Of course you can use any of the I2C chips available too. My >> philosophy is to adhere as much as possible to the KISS principle. >> >> On Wednesday, June 5, 2019 at 11:11:31 AM UTC-3, Keith Moore wrote: >>> >>> This is accurate and great detail. I believe it is simpler than you >>> might think. This is just a parallel interface (times two). >>> >>> The work is done with the shifters and the data is pumped via a parallel >>> interface from the processor as in the original design. >>> I am just a software guy, but once I saw the trusty parallel chip, I >>> figured it was a parallel interface. >>> >>> So how does one drive a parallel interface from Arduino/Raspberry? >>> Probably via a serial to parallel converter board with a variant of IEEE >>> 1284 output. I have not looked into this yet, but that's where I plan to >>> start. >>> >>> Am I way off base? >>> >>> On Wednesday, June 5, 2019 at 4:47:46 AM UTC-4, andybiker wrote: >>>> >>>> Hi John, >>>> The scans you posted answer all of the questions. >>>> There is no "display controller" as you'd expect from the modern "fruit >>>> machine" displays. >>>> All we have on the board is latches and level shifters. >>>> pins 16,18,19 control a shift register (TL5812) to select the digit >>>> position to display (both displays selected at the same time) >>>> there are then 4 latches - 2 for segments on top display, 2 for >>>> segments on bottom display >>>> These latch the 8 bit data bus (pins 4 to 11) to each level shifter. >>>> the first 3 latches are internal to an 8255 (antique i/o port that I >>>> last used in the early 80s) - selected with /A7 (pin3) low , /SEL4 (pin >>>> 13) >>>> low and /WR (pin1) low /RD (pin 2) HIGH >>>> A0 and A1 (pins 14 + 15) select which one of the 3 latches to use (and >>>> initialise the 8255) >>>> As this part only has 3 latches and we need 4, an extra latch has been >>>> bolted on in the form of IC2 (74ls273) >>>> This is selected with /SEL4 (pin 13) low, /A7 (pin 3) HIGH, /WR (pin1) >>>> low >>>> (I think reset should be kept high - need to check data sheets) >>>> Supplies are 47v, 5v, 4.5vAC for the filament. >>>> >>>> Data sheets are available for all of these chips. >>>> I suspect that driving one is "a full time job" for something like a >>>> simple arduino. >>>> >>>> I hope my ramblings help someone, >>>> Cheers, >>>> Andrew >>>> >>>> >>>> On Tuesday, June 4, 2019 at 9:52:24 AM UTC+1, Nixcited delighted wrote: >>>>> >>>>> I now have my displays and the schematic. >>>>> >>>>> I have scanned relevant manual pages, power supply, interconnect, >>>>> display board and component identification. >>>>> >>>>> https://www.dropbox.com/s/bltgd4w4o9gonuy/Alvin_G_Display.zip?dl=0 >>>>> >>>>> John S >>>>> >>>> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/ca3a1682-2f87-4f53-a4c5-40f55edbc587%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
