Electronics > Projects, Designs, and Technical Stuff
16 bit to 4 digit 7 segment decoder
<< < (15/16) > >>
obiwanjacobi:

--- Quote from: macboy on January 29, 2020, 05:50:15 pm ---
--- Quote from: obiwanjacobi on December 19, 2019, 08:27:08 am ---I have a (couple of) 4 digit 7 segment display module (NSB3881) and want to use it to plug into data and address buses of hobby projects to display bus values. The 7seg unit is common cathode and has all the segment lines (a-g/dp) connected over all 4 digits.

I want to make a self-contained module with a 0.1" header that can be plugged into breadboards (5V logic).

So I started to try to program a 2-digit version into a GAL22V10 (winCupl) but the segment mapping table generated too many product terms.
My other thought was to use a cheap micro (preferably Atmel/AVR - don't know PIC and don't have the programmer for it) to read the bus signals and output the 7seg data for each digit. It would need 16 (bus data) + 8 (a-g/dp) + 4 (digit common cathodes) = 28 IO pins. (would like a reset and an optional latch too => 30 IO pins).

Then I thought that perhaps there is a(nother) clever way to solve this problem and came here for inspiration.
Suggestions?

--- End quote ---

I'd say ditch the old display modules and just buy something new. For around $1 you can get a 8 digit 7-segment display which is controlled serially using a MAX7219-alike controller. Then a small cheap micro like Arduino Nano (etc) has just enough I/O for the 16 bit input and to control the display. The extra digits could be used to hold min/max values, display voltage read from an A/D pin, etc. Or use the vertical segments to display the raw bits (4 bits per 7-seg digit).

--- End quote ---

That may be the direction this would be going in the end. I did not fully realize how old these modules were and how much the LEDs have improved over the years. The initial idea was to use what I had and for now that will be sufficient (currently building one prototype on perf-board after trying it out on a breadboard) but when I need a couple of them I may well upgrade.

The initial question was more aimed at how to condense the logic needed for a 4-bit to hex-digit decoder. For the idea was to use a GAL to do the decoding. That could also still be a nice option (a lot of people would be happy with) - have a single chip that drives one digit on 4 bits of data.

Thanks guys, for sharing all your ideas.
SiliconWizard:

--- Quote from: obiwanjacobi on January 30, 2020, 07:26:31 am ---That may be the direction this would be going in the end. I did not fully realize how old these modules were and how much the LEDs have improved over the years. The initial idea was to use what I had and for now that will be sufficient (currently building one prototype on perf-board after trying it out on a breadboard) but when I need a couple of them I may well upgrade.

--- End quote ---

Yup, now that you settled for using a MCU, you could "upgrade" this using either more recent LED displays or even an LCD display instead, which would reduce power consumption a lot and could allow some fancier display.
obiwanjacobi:
Or one of those sexy small SPI OLED displays ...  8)

obiwanjacobi:
I've published my code and schematic.
https://github.com/obiwanjacobi/16BitDigits8515

Also finished the perf-board prototype that is working nicely.
Enjoy.
Benta:

--- Quote from: obiwanjacobi on February 05, 2020, 04:19:24 pm ---I've published my code and schematic.
https://github.com/obiwanjacobi/16BitDigits8515

Also finished the perf-board prototype that is working nicely.
Enjoy.

--- End quote ---

I'm still missing the common cathode drivers...

Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod