Controlling the 16 segment displays on PPDB

Retrobits

Hi there,

My PPDB is on the way (yippee), and I'm thinking through how to control the 16 segment x 6 LED alphanumeric displays.

Since there are 17 LEDs on each display (16 segments + decimal point) and 6 displays, I count 23 control lines required.· The Prop has 32 I/Os, so it doesn't leave me with much.

I have thought about putting another 40-pin Prop on the breadboard (with it's own EEPROM, XTAL, and transistor-based serial programming interface) to control the 16 segment displays, thus freeing the main PPDB Prop for other purposes.· However, all that is going to cost me a good amount of breadboard real estate.· Is there a better choice?

Naturally if I only need numbers, I could cut it down to 14 (8·+ 6) I/O lines.· But I'm sure I'll want the alpha capability...

- Earl

Timmoore

You could try a I2C expander e.g. PCF8574 or pcf8575 or a shift register 74HC595 they would give you extra output capability.

Oldbitcollector (Jeff)

Hey Earl.. Welcome to the party!

There's some code in this thread that might be useful.

Hows your Propeller Epson drive project coming?

OBC

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kensong

If (like me) you have a spare SX28 laying around; it fits directly on the board and:
1. Uses very little board space.
2. A minumim of extra components (1 x 10k resistor).
3. Is really cheap.
4. Gives you up to 19 lines to drive the displays with.

Then write to the SX using serial (Prop objects available), and just do a little display driver in the SX using
Beans' SX/B. The only limitation is the 19 lines, which won't drive the 25 (17+6) to do all the displays, but
it might get you going. The SX48 would, but doesn't come in DIP form.