setting up PIC32MX220 for PSP

setting up PIC32MX220 for PSP

Postby cncmachineguy » Mon Nov 17, 2014 2:07 am

This never got a peep on another forum, so I thought I would ask it here.. I have since moved on but the answer wil still be nice to know.

Seems like this should be easy, but having read all the info I can find, I still don't get how to make the hardware connections. I want to use the PSP to connect to a computer running in EPP mode. Here are the EPP signals:
D0-D7 =>data lines
read/write => 1 line to indicate read or write Input to PIC
Data strobe => indicates to PIC data is ready on the data bus
Address strobe => indicates to PIC address is ready on the data bus
Wait <= indicates to EPP port the PIC is busy or not
This seems like it should be so simple and probably is, but as I said - I must be missing something. Would someone tell me What pins to use for the control lines? I can sort out the reg's once I get this part done.

My main problem is this: I see seperate read and write lines in the PIC, but parallel port just uses 1. I also don't see the signal I should use for the wait. I thought about just using an I/O pin for this and controlling it through code, but this seems wrong plus I still have the read/write to deal with.
-Bert
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Re: setting up PIC32MX220 for PSP

Postby ric » Mon Nov 17, 2014 3:31 am

This is conjecture, as I've never used the PSP port on a PIC32.
One pin for R/W, and another for ENB, is "Motorola" format.
One pin for RD, and one for WR, is "Intel" format.
Looking in the PIC datasheet, it seems to only support Motorola format when in Master mode, not Slave mode.
You could convert Motorola signals to Intel signals using an external 74xx139 logic gate.

I'm not sure how you'd distinguish between Address Strobe and Data Strobe.
Latest test project, an LED matrix display made from one reel of addressable LEDs. here
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Re: setting up PIC32MX220 for PSP

Postby cncmachineguy » Mon Nov 17, 2014 3:44 am

WOW!!!
Liking this forum Much better! 11 months with no reply, and within hours I get a meaningful reply here.

Your answer is as I thought - no way to really use it as is. I just set it up in ISR and it works great - I get 500K transfers which is the limit from the PC. So I will store PSP in my head as maybe useful for board level comms, but not for PC stuff.

Thanks Ric
-Bert
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Re: setting up PIC32MX220 for PSP

Postby ric » Mon Nov 17, 2014 3:54 am

It stirred some ancient memories. I did an ECP interface to a PIC16F877 years ago, using the crude PSP that chip had. :)
Latest test project, an LED matrix display made from one reel of addressable LEDs. here
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Re: setting up PIC32MX220 for PSP

Postby cncmachineguy » Mon Nov 17, 2014 4:04 am

To be sure, I am only transferring a few (12) bytes every 30uSec or so, so no big task for my 80Mhz PIC. but still, it would be fun to be able to use DMA and all that jazz.
-Bert
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