Running a propeller hat standalone


#1

Firstly, many thanks to gadgetoid for his excellent installation scripts and tutorials on the Parallax propeller. With their help I have had a very enjoyable time exploring the unusual and somewhat quirky propeller hat.

I have reached the stage where I have put together a simple implementation of the old electronic Simon game which runs fine whilst the hat is attached to the RPi. What I would like to do now is detach the hat from the pi and run it ‘standalone’ supplying power via the 5v/GND connections on JP4. However when I attempt this the program doesn’t appear to start.

I have saved the program to the propeller from the IDE using F11 and have received a confirmation message saying it was verifying the EEPROM.

It is my understanding from reading the datasheet that on power up the propeller will initially listen in for communication on pins 31/30 before then attempting to load and run an image from the EEPROM. This doesn’t appear to be happening.

Before I start messing around with the reset pin and investigating further, I just wanted to check if what I am attempting is actually achievable and if so what I may be doing wrong.


#2

Thank you :D

Your understanding is correct

Which EEPROM IC are you using, do you have a wiring diagram for it?

How are you powering the standalone Propeller HAT?

This is the EEPROM setup I used successfully, although usually still slaved to the Pi: https://github.com/pimoroni/propeller-hat/blob/master/documentation/images/propeller-hat-eeprom.png

IIRC the reset pin is held high by an onboard pull-up resistor, so it shouldn’t be causing any troubles.


#3

Ah. Your question provides the clue I needed.

Possessing no previous knowledge of pi hats, and only having given a casual glance to the schematic, I jumped to the conclusion that the EEPROM on the board was thoughtfully provided by the nice people at Pimoroni as local non volatile storage space for the propeller. A more considered inspection of the signal naming, along with some research into the topic of pi hats, revealed the reality. Once again I have experienced the perils of premature assumptions.

Having dug out an old 24LC256, and using the diagram you linked to for guidance, I am now comfortably back on course to complete my homage to one of the early electronic game classics. Thanks once again Phil.


#4

Oooh yes, a few people have made that assumption. And I’m definitely of the opinion that the design would fare much better if the silly HAT EEPROM could be chucked in favour of an onboard 24LC256 for the Propeller itself. grumble

Glad you’re up and running, anyway! The Propeller HAT was very much a passion project, from my own interest with the bonkers chip.