Multiple Propellers loading from one eeprom

cbmeeks

I searched but couldn't find what I was looking for. Perhaps my search terms weren't that great.

Anyway, I was thinking about a circuit that has 2 to maybe 4 propellers. One propeller would be connected to an EEPROM as usual but when it booted, it would then copy 32K chunks to the other Propellers. Next, all of them would somehow get in sync.

Perfect sync wouldn't be a huge concern. But maybe something within a few microseconds. For example, one propeller for audio, one for video and one for I/O. All synced by maybe the NTSC refresh rate. Hope that makes sense.

So, is something like that feasible or would it just be easier (better) to put an EEPROM on each one and call it done? Those things are microscopic anyway. lol

Thanks!

Mike Green

Way back when, Chip published a Spin program to boot one Propeller from another (see attachment). The main Propeller behaves just like a PC and uses 3 I/O pins for Tx, Rx, and Reset for each "slave" Propeller. It takes a while to start up a Propeller although you could use a separate cog for each and start them up in parallel. The resting state for their receive lines is high (1) and the "slave"s (once they're all loaded and running) could all wait for the receive line to drop to low (0) which could be done simultaneously for all at once. That would synchronize them all.

These days, I'd just put a 64K (24LC512) EEPROM on each Propeller and be done with it.

cbmeeks

Thanks for the tip. Yeah, I will probably just use a dedicated EEPROM. It's amazing how quickly (even someone like me) can put a propeller on a breadboard, an EEPROM, a few wires for the PropPlug, and start developing.

You really don't need much at all. :-)

If I go simple and frugal in my design, I will only have one Propeller. If I go overboard and crazy, I may have three. So three EEPROMS it is. LOL

Thanks.

ManAtWork

I make a 5 channel stepper driver board which has two propellers on it. They both boot from the same EEPROM. Saving the $0.26 for the second EEPROM only makes sense for really big volumes but a side effect is that you also have to program only one EEPROM so this saves testing time.

I use a different aproach than Mike suggests. Both Propellers share the SCL and SDA lines. The master propeller holds the reset signal of the slave low until it has booted and started up, then it releases reset and the second propeller begins to boot. You don't need special software to boot the second chip, just one pin for the reset signal. If you pull this pin low at the slave you can also use it for the software to know in which chip it runs. This is useful if both propellers use almost but not exactly the same code.