Last night, while programming the LogoChip A6276 interface, I started to become concerned about having enough LogoChip pins to connect to everything I want to wire up to make the clock work. So I just did a quick sanity check to see whether I’ll have enough pins, or whether I need to double up digits together.
Here are the LogoChip pins:
| Available Pins |
|---|
| A0 – A2 |
| A3 – A5 ? |
| B0 – B7 |
| C2 |
| C6 – C7 |
I’m not sure whether A3 – A5 are available or not. They’re ghosted (grey) on the LogoChip sticker, and I’m not sure why. But because of that, I think I didn’t provide sockets for them on my Curiously Strong LogoChip, which may pose challenges while prototyping. Additionally, A0 – A2 didn’t work for driving the 6276, so maybe not even all of the available pins will work.
Anyway, here’s a tentative pin assignment.
| Chip | Lines | Count | Possible LogoChip Lines |
|---|---|---|---|
| A6276 LED driver | serial data in clock latch (each character) |
2 . 6-8 |
A0 – A1 (didn’t work) or B0 – B1 B0/2 – B8 |
| Dallas clock chip | data clock enable? |
2-3 | A0 – A2 (didn’t work for A6276) |
| PC serial port? | TD RD |
2 | C6 – C7 |
[Ewww, I don't like what the WordPress stylesheet does to the table text alignment.]
Looks like everything should work out, assuming that I can use all the pins the way I intended. In fact, if the clock is only six digits, I can use B0 – B1 for the 6276 data and clock lines and B2 – B7 for the digits’ latch lines, fitting the entire display driver into one I/O port. Tidy.
The Dallas timekeeping chip will need either two or three pins, depending on whether I use the DS1340 with I2C or the DS1302 with “simple” three-wire interface.
The LogoChip already connects to the PC’s serial port on pins C4 and C5; however, receiving data halts a running program. That means that while uploading control data to the LogoChip, although the real-time clock chip would continue to keep time, the display would freeze and stop updating; and that every data transmission would need to be followed by a command to restart the display program.
Since I may want to be able to send updates to the LogoChip while it’s operating (time corrections, commands to change display mode, etc.), I’m thinking of using the PIC’s built-in UART on C6 and C7 for run-time serial communication.
Anyway, the bottom line is that as long as I can figure out how to use the A port lines for digital I/O, and as long as we’re only making a six-character clock (HH:MM:SS without .TH), there are enough lines. Good deal.
Interesting to see what you’re up to. Hope you’re having better luck with the driver chips… They’re not terribly difficult to work with. My code wasn’t as complicated but I was able to pin point and light any specific LED I want using only the drivers and minimal outputs from the LogoChip. Of course, I had three 16-bit drivers which expanded the number of LEDs I could use and control. I have found that the output enable pin is very handy, especially to avoid ghosting. Your project should concentrate more on the software rather than the hardware, I think.
I hate Port A of the LogoChip. It must have something to do with the analog inputs. Have you tried disabling them?
Good luck!!