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Topic: Arduino and Raspberry Pi (Read 5505 times) previous topic - next topic

jimmis98

Jul 17, 2012, 10:14 am Last Edit: Dec 05, 2016, 12:50 am by jimmis98
First of all let me clarify that I don't have the required knowledge to make anything like what I'm proposing myself.
Second, please don't ridicule me because of what I may say.
Third, it's possible that I have posted this at the wrong place.
So, here we go:

If you take a look at this project http://dmitry.co/index.php?p=./04.Thoughts/07.%20Linux%20on%208bit, you'll see that taking a SIMM Ram and adressing it to an AVR microcontroller has already been done.
1st Part (and most possible)
I'd like to connect multiple 30-pin SIMM rams to an Arduino using probably some multiplexers and make Arduino able to use them. (yay, more ram)
2nd Part (and least possible)
I want to connect the Arduino to Raspberry Pi (A small Linux computer) and make it use the Ram
Alternatively, would it be possible to use the SIMM rams directly with the Raspberry pi by its GPIO pins? If I am not mistaken, the GPIO can be used as the arduino is used.

Can it be done?

PaulS

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I want to connect the Arduino to Raspberry Pi (A small Linux computer) and make it use the Ram

What does "it" refer to?

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Would it be possible to use the SIMM rams directly with the Raspberry pi by its GPIO pins?

As opposed to connecting it to the GPIO pins on the Arduino?

The art of getting good answers lies in asking good questions.

Grumpy_Mike

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I want to connect multiple 30-pin SIMM rams to an Arduino

There are many big problems with trying to do this:-
1) These are dynamic RAMs and so will need constantly refreshing at a rate much faster than the arduino can cope with.
2) The extra memory will not look like system memory, it will look more like the EEPROM memory. That is you send the device an address and it sends back the contents of that address.
3) This needs a lot of I/O, you will end up having to use an I/O expander of some sort like a collection of shift registers.
4) What are you going to do that needs that much storage?
5) Input / output speed will be limited.

Using the Pi, there are only 17 GPIO lines free. Basically the same sorts of problems occur.

Riva

What size/amount of RAM are you talking about and why does it need to be RAM? You can plug a USB drive into the Pi to give you lots of storage space but due to RAM size limitations you would have to page data from/to external storage. You would probably be better off looking at using a small form factor motherboard with a x86 processor if it must be RAM.
Don't PM me for help as I will ignore it.

Grumpy_Mike

That project make use of the fact that the 1284 chip has a architecture that allows some of the ports to be used as an external memory bus. The processor in the Raspberry Pi does not have that facility.

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If we can add ram on an avr (see the link on my first post), through some pins, why not do that on a Raspberry Pi.

Because there will be no way for the Pi's processor to access the memory as part of it's memory map. At best the memory is what is known as port addressed. It is of no use for running programs from.

AWOL

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If we can add ram on an avr (see the link on my first post), through some pins, why not do that on a Raspberry Pi.

Don't forget to make sure your SIMMs are 3.3V ones.
Oops, 3.3V 30 pin SIMMs don't exist.

Riva

#6
Jul 17, 2012, 03:16 pm Last Edit: Jul 17, 2012, 03:22 pm by Riva Reason: 1
The GPIO on the Pi has I2C & SPI breakout so you could potentially connect to an arduino with RAM module but there is no way I can see to map this additional RAM into the ARM memory space so you would only be accessing it like external storage. This coupled with the delays in write access Pi->arduino->RAM and read access Pi->arduino->RAM->arduino->Pi it would be far simpler to use a fast flash memory plugged into USB or a larger SD card with a storage partition/file.

Edit:
If it must be RAM and must be ARM then consider different board like http://uk.kontron.com/products/boards+and+mezzanines/embedded+sbc/pitx+25+sbc/ktt20pitx.html
Don't PM me for help as I will ignore it.

AWOL

You can use the SIMM as storage (like an SD card, or EEPROM),  but not as directly addressable RAM.

Grumpy_Mike

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but dont cut my head!

I don't think anyone is cutting your head. All we are doing are explaining the bits of theory that we feel you are missing.

So what if I said yes you can do that, I suppose you are then going to ask me how.

As AWOL said you can use memory like that to use as swap memory. But you have to find some way to tell Linux it is available and give it a way to access it.

What you are asking is not simple or straightforward.

wildbill

Although it doesn't seem so by today's standards, 256mB is still a lot of memory - far more than my first Linux box had for example. Do you have a specific requirement to solve that needs more RAM, or is this just an exercise to see how it might be done if you had such a problem?

dannix

Had to say this, just got shipping notification of my RaspberryPi I've been waiting 7weeks for it!

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