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Topic: New Dual ATMega Design (Read 12351 times) previous topic - next topic

JChristensen


With the avaliblity of these super cheap USB TTL serial cable modules...


@Lefty, I'm not aware of these, would you provide a link or two please?

CrossRoads

I do the same as I design it.
Unless you are usin parts with excessive plastic, things should fit.
I spread that are out a little more just in case.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

CrossRoads

Jack,
search for cp2102 on e-bay, there are tons of them.

The ones Lefty posted about last time  came in bags marked BU2001-020, also 214661-01N13d03.

These are nice because the pin marked RST can be cut easily and rewired to DTR.  I bought 3 of them, all were recognized by Windows Vista and it took care of downloading the driver. 
Seems to be marked www.betemcu.cn, cp2102 module, B75937
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

JChristensen

CrossRoads, thanx!  I also found some based on a Prolific PL2303, but they only seem to have four connections, power, ground, rx and tx.

CrossRoads

I have one of the smaller red ones also,

http://www.ebay.com/itm/USB-TTL-Converter-Module-buildin-in-CP2102-NEW-/230664868141?pt=LH_DefaultDomain_0&hash=item35b4b2912d

doesn't look to be very usable regarding changing Reset to DTR. Would be fine for building into something needing standard comm's tho. Came with a mini-CD, didn't need it after Windows had updated for the others.

Neither is pin compatible with FTDI basic, so a pin to pin adpapter cable wlll be needed using these kinds of parts
http://www.pololu.com/catalog/product/1905  holds the wires in the needed arrangement
http://www.pololu.com/catalog/product/1806  or
http://www.pololu.com/catalog/product/1930 and make your own.
I bought 50-packs of a bunch of these and bags of different size housings, this stuff has come on real handy for projects.

For example, adapting AVR ISP to ICSP on my Bobuino:


The Prolific parts are only USB1 I think. I think the CP2102 will do USB2. May not make a difference.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

JChristensen

So the CP2102 is similar to an FTDI FT232RL?

CrossRoads

Yes. Both are microcontrollers custom programmed to do USB to Serial using internal oscillator so no crystal.  Some models do use a crystal.
Like Arduino folks did with ATMega8U2 parts, using a crystal.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

JChristensen

Cool, thanks again. I do have some of those crimp connector housings and pins, but no crimp tool. Can make them work, usually, but is slow an tedious. Looks like the pre-made wires would be a good way to go.

CrossRoads

I bought pins too, have not tried hand crimping them. Got a lot of use from the 50-packs.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

bilbo

Neat board design! Hunkering down for a hurricane really does get the brain juices flowing. I'll be bringing my electronics to the basement tomorrow, should the need arise...

A while ago I designed a shield that had a second atmega on it, basically another arduino but in shield form, minus the FTDI. It had all of the headers from the bottom arduino broken out as well, and there was a jumper to select which arduino's serial port the FTDI was connected to. Essentially the same as yours, but modular. I imagine it could even be made stackable. A tower of arduinos! I suggested the idea and sent my design to sparkfun but they said they tried to avoid "arduinos on arduinos", which makes sense, I guess. It was worth a try! Im sure I have the schematic somewhere...

Stay safe,

CrossRoads

Thanks :)
With the low prices of boards from iteadstudio, I'm willing to take a shot at building some of these things up just to play with.
Where as before, I would only build something if I had a specific project in mind, outside of that was just occasional playing on solderless breadboard.

Between the IDE, the uCs, and cheap prices, its like a breath of fresh air in my hobbying.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

bubulindo


No, two processors could never decide which one of them is the insane one.

True, Siemens H-PLC system will only notify if one of the PLCs went bad, but the one running as master will keep doing so. If the master stop,s the other will take over (almost) immediately, but with careful programming no problems arise.


You need triple redundancy and then just vote on who is the insane one, 2 out 3. The highest security PLC system we used in the refinery were made by Triconex, used triple redundant processor boards, dual redundant I/O boards, dual redundant and battery backed up power supply modules. It was a beast, looked like something you would mount on a aircraft carrier and boy was it expensive! Made to mil spec standards. Funny thing is that 'baby sitting' one for ten years in my plant area I never saw a single failure alarm signifying a loss of redundancy, so all the redundacy were never called into practice.


Any chance I can get a trip to see it? :$ Yes, I'm a geek and would love to see that setup.

Just because the redundancy never came into place, doesn't mean it was/is a waste... give it enough time and eventually it may pop up. :)
This... is a hobby.

mnmis

CrossRoads,

On the schematic it says that one processor supplies the clock to the other processor. I see the single crystal but I don't see the connection between the processors for supplying the clock. That would be a good feature to add.

Mnmis

retrolefty

#29
Aug 28, 2011, 03:44 pm Last Edit: Aug 28, 2011, 03:47 pm by retrolefty Reason: 1
Any chance I can get a trip to see it? :$ Yes, I'm a geek and would love to see that setup.

No, I retired four years ago and even I can't get back in. Here is a pretty nice document explaining
the design and methods they used to attain the various redundancies:

http://www.dia.uniroma3.it/autom/Reti_e_Sistemi_Automazione/PDFseminari/TRICON%20Fault%20Tolerant%20Systems.pdf


Just because the redundancy never came into place, doesn't mean it was/is a waste... give it enough time and eventually it may pop up.

Certainly, the system was the emergency plant safety shutdown system, it worked independently from the plant process control system. This plant ran 24/7/365 for up to 4 year runs before scheduled shutdowns. A 'false' safety shutdown would be very costly as the plant lost profit could exceed 1 million dollars a day, and it often took 2 days to restart up the plant depending on the cause of the trip. However failure to trip off on say a large compressor failure could result in compressor damage taking months or longer to have critical parts manufactured as compressor was built to order and there is no such thing as a 'shelf spare'. The price of the safety systems was almost inconsequential as long as it performed it's function when called upon.

Lefty

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