Looking for simple way to interface BCD to serial (RS232)
in [Design]
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From: Joerg on 29 Dec 2009 18:35 don wrote: > Joerg wrote: >> don wrote: >>> Joerg wrote: >>>> Martin Riddle wrote: >>>>> Datasheet <http://www.intersil.com/data/fn/fn3167.pdf> >>>>> >>>>> Sync the digits with the Mux outputs. >>>>> >>>> >>>> But that could present a problem. Converting parallel to serial is >>>> easy but now he'll have to work with a bit rate that's probably >>>> non-standard. Or he could try to change the mux rate until it gets >>>> to within a percent of a popular baud rate while keeping potential >>>> drift in mind. >>>> >>> >>> It was stated in an earlier post about the update rate and baud rate. >>> >>> The OP stated that the display update is 300 updates a second. >>> >>> There are four BCD digits, so it take about 3 mSec to scan one set of >>> digits. >>> >>> Looking at the diagram on page 2, the digit drivers and the BDC I/O >>> are all is needed to capture the numbers on the display. >>> >>> A software loop checking each digit driver and assembling a ASCII >>> string in an output buffer. >>> >>> And if the display changes, send the ascii string out the serial port >>> ( any baud rate). >>> >> >> Ok, yeah, you could send out 19.2k or faster bursts. But I don't see >> how that can be done without some uC programming up there. Which the >> op said he doesn't want unless it can be had on a silver platter :-) >> >> >>> My question would be on the PC side. >>> How fast can a PC process data before its buffer overflows ? >>> >> >> IME a modern PC with a decent terminal program doesn't choke at all. >> Same if it pipes into Excel (BTDT). >> >> >>> Do I care, will the PC guy understand that he may drop data. >>> >>> The worst case would be if the lowest digit changes every update. >>> >>> don >>> >>> PS: with the ICM7217 out of production, how would someone test if >>> this works with out the original unit ? >> >> >> AFAIU the op already has the units with that chip in there. >> > > Looking more at the data sheet, just using a PIC as the counter would be > the easiest. > > Knowing how this ICM7217 is configured and using an interrupt on the PIC > counter. > Sure, but the OP wrote, quote "I don't want a software fix unless I can do it in PicAxe and can find code written." So the 1st part would probably be quite feasible (but I don't know PIC-Axe), the 2nd part is doubtful unless someone had the same task at hand before and has posted the code. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Fields on 29 Dec 2009 18:59 On Tue, 29 Dec 2009 11:59:27 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Martin Riddle wrote: >> <don> wrote in message >> news:Kq-dnfM2ZeS7taXWnZ2dnUVZ_rdi4p2d(a)forethought.net... >>> Martin Riddle wrote: >>>> "Joerg" <invalid(a)invalid.invalid> wrote in message >>>> news:7pqjftFe4cU2(a)mid.individual.net... >>>>> RFI-EMI-GUY wrote: >>>>>> don wrote: >>>>>>> RFI-EMI-GUY wrote: >>>>>>>> I have a device that has a three digit LED display. The chip that >>>>>>>> drives the LED also has four Binary Weighted outputs (1,2,4,8) >>>>>>>> and three address pins for 100's, 10's and units. I want to drive >>>>>>>> a FIFO UART of some sort to output an RS232 stream so that this >>>>>>>> device can update a software program. Baud rate 300 to 4800 range >>>>>>>> would be nice if possible. >>>>>>>> >>>>>>>> The updates are about 300/second >>>>>>>> >>>>>>>> Is there a real simple hardware FIFO UART that can do this >>>>>>>> without a lot of extra hardware. I don't want a software fix >>>>>>>> unless I can do it in PicAxe and can find code written. >>>>>>>> >>>>>>>> Off the shelf products OK I don't want to reinvent the wheel. >>>>>>>> >>>>>>> Do you docs on the outputs ? >>>>>>> >>>>>>> don >>>>>> I think you are asking the specs of the driving chip? Its an >>>>>> ICM7217IJI Common Cathode 4 LED Display/Programmable Up/Down >>>>>> Counter. The BCD I/O pins and the segment drivers b, d and f (d1, >>>>>> d2, d3) used to select 100's. 10's and units (I may have order >>>>>> reversed). >>>>>> >>>>> That will not be so trivial because this is a chip that drives the >>>>> LED in muxed fashion. >>>>> >>>> There are separate BCD outputs, in addition to the LED drivers >>>> abcdefg. >>>> So he could use the muxs to latch the bcd data into shift registers. >>>> After 16 bits are latched, clock them out with start and stop bits. >>>> >>>> Cheers >>>> >>>> >>> This is what I was wondering about. >>> >>> So my answer is "use a PIC". >>> >>> As long as there is a way to sync with the first digit, that with >>> would be easy. >>> >>> don >> >> Datasheet <http://www.intersil.com/data/fn/fn3167.pdf> >> >> Sync the digits with the Mux outputs. >> > >But that could present a problem. Converting parallel to serial is easy >but now he'll have to work with a bit rate that's probably non-standard. --- Not necessarily, since if he uses the digit strobes to acquire the BCD data, one digit at a time, in parallel, and generates the start and stop bits at the same time, he'll have the time until the next digit strobe to shift the ten bits out, serially, using a bit clock his receiver is expecting. --- >Or he could try to change the mux rate until it gets to within a percent >of a popular baud rate while keeping potential drift in mind. --- Much easier, I think, to just shift the data out using the proper bit clock assuming, of course, the receiver is fast enough to receive ten bits between digit strobes. JF
From: don on 29 Dec 2009 20:01 don wrote: > > PS: with the ICM7217 out of production, how would someone test if this > works with out the original unit ? Looks like it is still in production, just not from intersil.com . http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1501 don
From: MooseFET on 29 Dec 2009 20:59 On Dec 29, 8:25 am, Don Lancaster <d...(a)tinaja.com> wrote: > MooseFET wrote: > > On Dec 28, 6:48 pm, RFI-EMI-GUY <Rhyol...(a)NETTALLY.COM> wrote: > >> MooseFET wrote: > > >> snip > > >>> I think it would be easier without the FIFO UART. You just want a > >>> signal that looks like the RS-232. You don't really need a RS-232 > >>> receive function at all unless you want to use it to set the Baud > >>> rate. > >> I need compatibility with software that expects RS232 , I need to send > >> the appropriate bits, although the RX could be used to program the PIC I > >> guess. > > > Yes you need to be compatible with software that expects RS-232. This > > means that you do not need a UART chip. All a UART chip does is make > > a signal wiggle up and down with a certain pattern. It is often > > easier to just make the signal you want rather than adapt to some > > chip. > > > Example: A simple counter driving a 4051 MUX or two or three can make > > perfectly good RS-232 data out of some small collection of logic > > signals. > > Use a PIC instead of pissing around. I don't know that RFI-EMI-GUY knows how to program one. Without a program they are fairly useless. The 8051 is better anyway. You can get a nice version from Silabs. > > -- > Many thanks, > > Don Lancaster voice phone: (928)428-4073 > Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 > rss:http://www.tinaja.com/whtnu.xml email: d...(a)tinaja.com > > Please visit my GURU's LAIR web site athttp://www.tinaja.com
From: Jamie on 29 Dec 2009 21:21
RFI-EMI-GUY wrote: > whit3rd wrote: > >> On Dec 27, 1:52 pm, RFI-EMI-GUY <Rhyol...(a)NETTALLY.COM> wrote: >> >>> I have a device that has a three digit LED display. The chip that drives >>> the LED also has four Binary Weighted outputs (1,2,4,8) and three >>> address pins for 100's, 10's and units. I want to drive a FIFO UART... >> >> >>> Is there a real simple hardware FIFO UART that can do this >> >> >> The RS-232 requirement will be somewhat awkward, depending >> on what power supplies are available; have you considered >> USB instead? The FTDI device "FT245R" is a FIFO-input >> USB slave device, with software support. I'd imagine you >> can clear the FIFO and clock eight bits of address-and-BCD >> data (four BCD bits and three 'digit enable' flags) as the >> display is updated. Maybe the 'extra' bit could be used for >> overflow or other error indicator. > > > I understand that I may need a bi-polar power supply and line driver > like a DF1488 am wary of USB beacause I don't know if any of the legacy > amateur software that this will be used for has drivers for USB. Tell me > more however. > you can use a USB-RS232 converter, the old software will work. P.S. Beware of Windows 7, it don't want to run 16 bit apps with out a VM for Xp on it. Up todate, I've only seen 64 bit versions of W7, there could be 32 bit versions, who knows! |