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A PET storage option

gubbish said:
To get .prg files onto the card, you just connect it to a computer, format the card with FAT32, and copy the .prg files into the root directory. When you put the card back into the PETdisk, the PET can see the files.
Click to expand...

gub,
This beats the way I am currently transferring files from a PC to the PET, so yes I want one.
-Dave
 
MikeS said:
Just out of curiosity: how are you currently doing it?
Click to expand...


I have a 4040 drive on the PET and a 1541 drive to a parallel port on an old PC using an XM1541 cable. Running Star Commander under DOS, I copy files to/from the 1541 diskette. I then insert that floppy into the 4040 and LOAD the program file into the PET. The 4040 and 1541 are read compatible.

I have to remember to then SAVE the file on a 4040 formatted diskette. If I SAVE files from the PET to the 1541 formatted diskette, it may corrupt it.

The 4040 is getting tricky to maintain. It has a dual CPU design that shares the data bus and RAM so troubleshooting is a little involved. Its 2332 ROMs are wired such that they are not compatible with the 2532 EPROM (although they are somewhat compatible with the 2732). Anders sent me a mechanical part to fix it the last time, but one day it will buy the farm.

So you see, I am looking forward to trying these SD gadgets.
 
Ok Dave, you're on the list. I'm in the process of assembling the boards this week and double checking for any software bugs I might have missed. Will keep you posted on the details, I should be ready to send these out early next week.
 
Will you be offering them as board only, kit, or fully assembled?
I'd certainly be keen on getting one (or possibly two) regardless of how they are offered. However I want to install one on my PET board that is mounted in a suitcase and there are some space restrictions. I may have to mount the tape connector at 90 degrees for it to fit so fully assembled may not work for me.

Cheers
 
I can provide them in any of these forms, whatever you prefer. PET in a suitcase sounds great, I'd like to see a picture of that. How much clearance do you have behind the tape connector?
 
Impressing small solution!

But I'm wondering how you solved the 5V vs. 3.3V issue?

Following the specs SD cards are allowed for 3.6V max but USB/cassette port gives you 5.0V. If you run the AVR at lower voltage to safely communicate with the SD card, you'll exceed the max voltage at the ports connected to the IEEE bus working at TTL levels (up to 5.0V). AVRs aren't 5V-tolerant when driven at 3.3V. I beleave it works for you but to me it seems like a dirty hack at the price of risking to toast some cards.
 
Thanks!

I am running the AVR at 5.0V, and the SD card is actually protected by 4 3.3v Zener diodes. The pins on the SD card which need such protection are Power, /CS, Data in, and clock. Data out from the SD card is connected directly to the MISO pin on the Atmega8, which is configured as an input always, so this pin does not need a zener as it is always just an output from the SD card. On the SD power pin, there is a 20 ohm resistor to limit the current going through the zener. I chose this resistor value to provide enough current for the SD card. 1.7v drop / 20 ohm = ~85mA. I've looked around for specs on the current consumption of SD cards, and I've seen various numbers from 20mA to 100 or 200mA consumption for SD cards, but this has worked for every uSD card I've tried so far.
 
gubbish said:
Basically I soldered a 7-pin header onto a MicroSD-to-SD adapter. So a microSD card goes into this adapter to serve as the storage for the PETdisk.
Click to expand...
I'll say it again: what a great idea, especially when I read about the problems folks with other SDcard projects are having finding cheap and compatible sockets. I'm going to steal it for a little uSD project I'm planning; hope I don't have to pay you royalties ;-)
 
Posted some demo videos of the PETdisk doing its thing.
These are not going to win any cinematography awards, but hopefully they are interesting. :)
Part 1:
Part 2:
 
Hi again,

I've tallied up the prices for the various flavors of PETdisk that will be available.
Right now, the boards I have on hand are all spoken for, and I have about 3 requests in for the next batch.
The exact price will be determined by the size of the PCB run. Assuming a run of 10 boards, here are the prices:

Board only: $11
Kit (PCB, programmed MCU, and all parts): $20
Fully Assembled & tested: $30

If we get 20 boards, these all drop by $3.

So let me know if you're interested and you'll be on the list for the first new batch of boards. I'll be PMing the early adopters who are getting the first 3 units. Thanks!
 
Also, if you do decide to get the board, I recommend getting an AVR programmer so you can update the firmware on the Atmel MC for fixes and updates. And microcontrollers are lots of fun so I say try it out. I found a couple of options for this that are fairly inexpensive.
Here's a USB programmer kit: https://www.adafruit.com/products/46&zenid=e92c608579787989a1def11eba606f6e

And here's a super bare bones one, just a serial connector and some diodes/resistors: https://www.adafruit.com/products/26&zenid=e92c608579787989a1def11eba606f6e This one requires the circuit to be separately powered though.

I have not personally tried either of these, but I will probably get one or the other to try it out.
 
Very sweet. I'll definitely get one!

I have an AVRisp MK II, so I should be good to go on programming.

-Twylo
 
Twylo said:
Very sweet. I'll definitely get one!

I have an AVRisp MK II, so I should be good to go on programming.

-Twylo
Click to expand...
Don't you give up on yours, though!

Am I right that Mike's deals with individual .PRG files whereas Seth's uses image files?
 
dave_m said:
gub,
The demos are great. Out of curiosity, does the PETdisk respond properly to the BASIC 4 commands of "directory" or "catalog"?
-Dave
Click to expand...

It does not at the moment. But I would like to support these in a future revision. Do you know how these commands work on the IEEE-488 bus? I could just watch these commands on the bus but would certainly be easier to implement if I knew the sequence. I've mainly been working from the "PET and the IEEE-488 interface" book, and these commands are not documented there.

Another upgrade which will go into the next revision will be support for long file names when saving files to the PETdisk.
Currently when saving a file to the PETdisk, you are limited to a short DOS filename (8.3), and since it gives every file a .prg extension, you're really limited to 8 characters. (i.e. 'SAVE "12345678",9) This limitation is only when saving a file - with loading you can read files with long filenames. This is because I currently have code that can read long file name attributes in the FAT32 file system, but do not have code to create such attributes yet. This is next on the agenda. You can, however, rename them with long file names on your computer after they are saved from the PET, and you can read them back with the long names.

The last revision I put into the firmware was support for hot-swapping SD cards - so you can remove a card from the PETdisk, change some files on your computer, then put it back in, and it will recognize the changes.

One other thing - I found this schematic for a very simple serial port AVR programmer. This looks equivalent to the link I posted earlier, but this is a homebrew version. A very simple way to get set up for programming AVR chips, if so inclined.
http://avrprogrammers.com/bld-dasa.php
 
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