Digital Output Signals on TI

[coolio]

I have been creating some LED matrix projects being driven by an Arduino ( example project ), but I was wondering if I could drive the LED matrix with my TI instead. What I am seeking is advice on is where would be a good point to get a controllable +5V digital signal? I am using 74HC595 shift registers to control my LED matrices, so I would just need 3 digital line: the serial signal, a clock signal, and a latch signal.

 

Can this be done via the side port? The cartridge port? I remember from the 80's there was a project to create an RS232 device through the joystick port, is that another option? Is there an design for a GPIO-like card for the PEB?

 

Thanks for any pointers to help me get started with this project!

[Stuart]

You can get two independently-controllable signals direct from the joystick port, but I don't think it will do three. A couple of options spring to mind:

 

(1) Use the joystick port as an I2C interface. See http://www.stuartconner.me.uk/ti/ti.htm#i2c_interface. Connecting something like a PCF8574 (http://cache.nxp.com/documents/data_sheet/PCF8574_PCF8574A.pdf?pspll=1) will give you 8 controllable output bits.

 

(2) Connect a TMS9901 to the side port. See http://www.stuartconner.me.uk/ti/images/eprom_programmer_circuit.pdf. This will give you lots of input/output bits.

 

(3) The UberGROM cartridge has 6 digital GPIO pins that can be configured as input or output. Not sure if anyone has actually done anything with these yet, so you may be breaking new ground!

 

You'll need to do your code in assembly to get anything near decent speed if you're strobing through sets of LEDs.

[+jedimatt42]

If you are not using any other side port peripherals except memory expansion, this is basically the schematic I did to mimick ElectricLab's KITT demo on the side port.

 

https://github.com/jedimatt42/pi-messaging/blob/master/schematics/TI-RPi-interface-r1.pdf

 

You can expand it by decoding other addresses and latching writes to them.

 

This version has no CRU bit controlling if it is mapped in or not, so it is easy to drive from any enhanced basic that has CALL LOAD. I believe this MiniMemory BASIC code went with that schematic:

https://github.com/jedimatt42/pi-messaging/blob/master/comm/comm_mm.bas( It is sort of half of a terminal program )

 

I had the KITT side to side setting of a bit written in basic, and it didn't need any delay code at all So, as Stuart said, you'll want a faster language for anything animated. Although the effect of a Slow basic building the image could be cool.

 

Warning: I programmed some GAL16v8's to do these things ( the WinCUPL source is near there. ) So I've not tested the chip selection in the schematic.

 

An aside:

I think it would be really cool to have a LED Cube, that 'wire-taps' the TI address bus, and over times shifts snapshots back through the depth of the cube, creating sort of a heat-map...

 

-M@

[coolio]

Thanks. I will look into these ideas and see what I can do. I may be asking for some help once I figure out a path.

[+Vorticon]

Here's another option for you using the parallel port:

http://atariage.com/forums/blog/659/entry-13589-parallel-port-interfacing-using-extended-basic-on-the-ti-994a-computer/

[Opry99er]

Hey Walid, that link above did not work for me... Is it working for you?

[+Vorticon]

Hey Walid, that link above did not work for me... Is it working for you?

Sorry. Fixed.

[Opry99er]

Hey thanks!!! Looks like some excellent info in there!

[Opry99er]

Wow... That is an excellent set of routines there!!

 

Thanks!!