4 digits display to a 12F683

[Tarsil]

Any ideas about the easiest way to conect a 4Dg display to a 12F683?
I'd realy like to use this chip so...no way I'm using a biger one.

 

[Nigel Goodwin]

Any ideas about the easiest way to conect a 4Dg display to a 12F683?
I'd realy like to use this chip so...no way I'm using a biger one.

Fairly obviously you don't have anywhere near enough I/O to drive four 7 segment displays, so you need some kind of driver to do so.

Probably the easiest solution is to use a 16F628 to drive the displays, fed via a single serial connection from your smaller PIC. There are various chips you can use to interface to LED's, try Maxim and see what they do?, but it's probably more expensive and larger than a 16F628, and most likely requires more connections than the one a 16F628 would need.

 

[Tarsil]

The idea is that i'm planing to build a smart&cheap batery charger in several pieces. The price is an issue so I'm craming some code in a 12F683 wich has AD imput (primitive but enought for the purpose). I have to display 4 digits meaning number of cells, discharge&recharge mode and current used.
Realy need a AD imput&need to cram the hole circuit in a small box .

 

[Tarsil]

I'd have like 4 pins left. Any cheap multip/demultip chips?

 

[manish12]

i.e LED = cell in your case.
right or wrong ?
if it is so ! than nice idea .
i dont konw , what i got ? , if i am right , than you have to think about charging current.

 

[hjames]

It's been mentioned before: "charlieplexing". The Maxim chips are expensive, but the idea is free:
**broken link removed**
- you only need 8 pins to drive that display.

Alternatively the '595 style logic chips are serial in-parallel out registers with latches, but you'd still need ~4 IO's to drive them.

Maxim also makes some small chips that can be used as 2-1 mux/demux's. The smallest "common" parts are in the 4051/4052/4053 family. These are all 16 pin parts (although you can get 16 pin tvsops which have .4mm pin pitch).

 

[penoy_balut]

if you have four pins left, use the two for serial to parallel chip like shift register to drive the segments and the other two for shift registers driving the 7 segment commons, you can have as many seven segments as you want, displaying numbers use scanning algorithm.

 

[Tarsil]

i.e LED = cell in your case.
right or wrong ?
if it is so ! than nice idea .
i dont konw , what i got ? , if i am right , than you have to think about charging current.

Well...not quite. One digit is for diplaying the number of cells (is for NiCd&NiMh) eq.2,5....Another digit is for displaying C&D (charging and discharging). Digits 3&4 are for diplayng current ..eq. 05 (.05A), 20 (.2A) and so on.

 

[Tarsil]

Hmm...1 pin for AD in, 1 for reset/program (the one that's imput only)....gives me 4 pins to play with. The 595 idea is great...I'l start craming some code into the PIC...when I have some time.
The 595 is cheap enought!

 

[Tarsil]

BTW...Does someone knows a uC (pref a PIC or 8051 clone) that has a 10 bit AD, a comparator,2k+ of flash and more than 8 pins?
And.....under 2$

 

[Tarsil]

And PWM

 

[Madhouse]

**broken link removed**

Take a look at this, it isn't a "cheap" solution but might give you an opportunity to save time/money/work elsewere. And in a 16PDP isn't too big either - especially as you can get some of your spare I/O pins "back".

 

[William At MyBlueRoom]

Sorry just had to pipe in.

I've yet to meet a Micro designer that doesn't like to use the smallest PIC possible for their project. They almost all claim cheapest is the motivation but in fact I'm willing to bet bragging rights is the real motivator (Guilty)

That said, if you're really looking to keep the cost as low as possible then...

Don't use an 7 Segment display, with a little a 3 I/O pins you can display 6 LEDs (Most chargers only have a single LED anyway) with 4 I/O you can display 12 LEDs. Look on Microchips site for Tips & Tricks in the app notes section. (great reading too)

Use a PIC with enough I/O to get the job done with as little glue logic as possible. There are 100s of PIC choices, you can almost always find one that fits the bill.

One very old but application specific chip that comes to mind for battery charging apps is the PIC14000

But it's not cheap, so lets see a PIC16F716 has A/D & PWM (enhanced too) and a volume production price of $0.73 and enough I/O to run a MAN6740 display in Charlieplex mode (8 or 9 pins with dp).

Just thought of this, not tested but should work...
**broken link removed**

 

[tunedwolf]

maybe you could use the UCN5818 from Allegro...should be able to squeeze that into the I/O you have left...

 

[Tarsil]

Ok...maybe a bit of bragging rights :lol
The 16F716 isn't to be found localy. I'd have to order it from Germany (nearest) and for 20 pcs....isn't worth the price. The charger is for NiCd and NIMh bat and discharge the bateries until 1V+/cell THEN starts the charging proces. The curent and number of cells also is changed in a "set mode". I'd realy need at least 3 digits if not 4.
A alternative whould be the cheap (and more pin counts) 89C2051 but it doesn't have a AD.
Third of all I'd realy like to use some boxes I have.

 

[Tarsil]

**broken link removed**

Take a look at this, it isn't a "cheap" solution but might give you an opportunity to save time/money/work elsewere. And in a 16PDP isn't too big either - especially as you can get some of your spare I/O pins "back".

Maxim has a chip for everything but usualy on the expensive side. At that price I'd buy a 16F877A with a lot of goodies.

 

[Nigel Goodwin]

Your problem is basically down to wanting to use the wrong PIC in the first place - by choosing a suitable one all your problems are solved, and your chip count is reduced.

 

[Tarsil]

The next chip I could buy&use is a 16F877A. In the boxex It whould be OK to put a 12F683 and 2X595IC but a single 877A...whould be a problem due to the size&shape of the boxes (i'l have to cram inside a radiator, some power electronics etc.).

 

[eng1]

BTW...Does someone knows a uC (pref a PIC or 8051 clone) that has a 10 bit AD, a comparator,2k+ of flash and more than 8 pins?
And.....under 2$

Well, you don't know the PIC16F684? It has 10 bit ADC, 2 comparators, INTOSC, 12 I/O pins, 2k flash memory, PWM. I don't remember its cost. Great micro controller!

EDIT: as suggested, you can use a 4511 to drive the displays

 

[Nigel Goodwin]

The next chip I could buy&use is a 16F877A. In the boxex It whould be OK to put a 12F683 and 2X595IC but a single 877A...whould be a problem due to the size&shape of the boxes (i'l have to cram inside a radiator, some power electronics etc.).

16F88, 16F819 (18 pin) - there are plenty of suitable smaller chips available, or even a 16F876 (28 pin).