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Linking 2 MCUs: I2C, SPI, or a Home Grown Interface?

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Max The Magnificent
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Re: Cow and Horse Manure
Max The Magnificent   4/30/2014 9:53:29 AM
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@Douglas: ...the pay-scale just didn't compensate for some of the risks involved...

Exploding containers of animal feces is certainly a risk most of us don't face in our daily jobs :-)

Max The Magnificent
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Re: Cow and Horse Manure
Max The Magnificent   4/30/2014 9:51:57 AM
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@Douglas: So... if you dilute these substances for ease of application, or not, do NOT place them into any tightly sealed containers. Especially any glass jars or bottles.

Sound advice, old friend. In fact I have the two tests of brass embedded in cow and horse manure in seperate plastic coffee containers with plastic lids, each with the tinyiest of tiny holes in the top to relieve the pressure, the whole kit and caboodle then placed in a big black plastic bag (and hidden from my wife in the corner of the garage LOL)

halherta
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If it ain't broke......
halherta   4/30/2014 8:10:11 AM
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Max,

For your particular application (ATMega as Display Driver & and a 32-bit Micro/FPGA for audio sampling and possibly FFT) I'd use a UART. The ATmega should have at least one UART and the FPGA/32-bit Micro will very likely have multiple UARTs. 

All handshaking can happen in software over the TX/RX pins and transfer speeds of 1Mbps should be achievable on the ATMega and FPGA/32-bit Micro.

The other possibility ..especially if higher transfer speeds are required is to use  SPI. Again SPI is an established protocol and works well for this sort of thing.

I2C was designed for use in a scenario where a master device needs to communicate to many slave devices (same with SPI, but SPI is OK for maybe upto 5-10 devices whereas I2C can handle hundreds of slave devices ) over only two wires. This I2C bus speeds are typically be slow with a Maximum bus frequency of 400KHz.....though SMBus can reach 1MBps as well....but the ATMega's TWI(I2C) interface is not capable of doing SMBus transfers.

 

I think that UART and SPI are ideal for this sort of thing. Coming up with a custom protocol can be fun, but is unnecessary and will require a larger time investment to get it right.

 

Douglas442
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Re: Cow and Horse Manure
Douglas442   4/30/2014 12:23:07 AM
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Max,

Glad to see the progress that is being made on this project. Might we be able to hope that the final product, on the DSP and interface side, might become a kickstarter project? A visually appealing and low-cost audio-spectrum analyzer, of this sort, would certainly come in handy.

However, on the purely cosmetic side of the thing, please be careful. The reason why I'm replying to your first comment is to issue some cautionary advise. I only hope I'm not too late...

In my former occupation as a lab technician I had once worked at an agricultural laboratory where, in addition to analyzing soils and irrigation waters, we also had the occasion to work with such delightful stuffs as you are working with, here. So... if you dilute these substances for ease of application, or not, do NOT place them into any tightly sealed containers. Especially any glass jars or bottles.

On one occasion, our lab had received the waste-water run-off from a local dairy facility. It was sampled into a large sealed glass jug in which it sat waiting for several hours before processing. Luckily, I was nowhere nearby at the time... but a co-worker standing next to the jug suddenly began to hear the sound of cracking glass...

Fortunately... he had been in this line of work long enough to have developed some reflexes... immediately hitting the floor mostly saved him from being drenched by the awful stuff. All the rest of us only had to put up with the smell.

As I said, this was a "former" occupation... as, for one thing, the pay-scale just didn't compensate for some of the risks involved.

Ancient reminiscences aside, as an alternative to working with such hazardous materials in order to achieve the desired metallic finishes on your future projects, you might want to give these folks a call:

http://www.luminore.com/



Max The Magnificent
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Re: What about USB?
Max The Magnificent   4/29/2014 5:41:34 PM
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@stwomey0: Many small processors, even PSoC, have USB interfaces on them...

Good point, but I have to admit that I'm quite looking forward to playing with my own little home-grown interface...

stwomey0
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What about USB?
stwomey0   4/29/2014 5:39:42 PM
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Many small processors, even PSoC, have USB interfaces on them.  The protocol is easy to use, you can set the polling rate, and the electrical intrface should be agnostic to 3.3/5.0 volts.  The drivers are usually included in a BSP and there are many web sites to assist: http://janaxelson.com.

Max The Magnificent
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Re: Arduissimo: MultiCore Arduino enables Virtual Peripherals
Max The Magnificent   4/28/2014 10:24:43 AM
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@Tobias: Maximus ! The good thing is, that there is a great solution right around the corner. A MultiCore Arduino optimized for Virtual Peripherals...

Good luck with your Indiegogo project -- email me directly when it launches and I'll bounce over to take a look at it.

Max The Magnificent
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Re: re
Max The Magnificent   4/28/2014 10:22:20 AM
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@prabhakkar: In electronics domain 15 years are like 50 years.

Ah... That explains why I feel like I'm 150 years old LOL

Max The Magnificent
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Re: Long term consequences of Design decisions
Max The Magnificent   4/28/2014 10:20:55 AM
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@Sanjib: The lesson that I have learned from this: Whenever there is a non-standard, not so popular interface is used to do something quicker that point of time in short term, there remains a high risk for the need to redo things in long term when that special/unique interface is obsolete.

That's a good point -- but in this case I will probably only ever build this one display, and the great thing about my "bare metal home grown interface" is that it's so incredibly siimple.

Also -- if the truth be known, it's fun making your own interface LOL

Max The Magnificent
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Re: DMA or SERDES
Max The Magnificent   4/28/2014 10:18:08 AM
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@_hm: For wider bandwidth, I prefer SERDES...

I agree -- but I'm nowhere near needing that amount of bandwidth (thank goodness LOL)

 

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