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Topic: New Dual ATMega Design (Read 12401 times) previous topic - next topic

CrossRoads

Aug 27, 2011, 07:41 am Last Edit: Aug 27, 2011, 08:09 am by CrossRoads Reason: 1
Check it out!
Dual ATMega 1284 (can be 324, 644, 1284)
ICSP Interface each device
JTAG Interface each device
2 RS232 Ports with 3-pin headers to go to DB9 connector for each device - 4 RS232 ports!
Can select via jumper to use port as TTL Serial, or connect to USB/Serial
USB Programmer Header each device
Activity LED each device
+5 Regulator Power on LED
+5 Power selectable for each device - USB Programmer, Regulator, off Board
Reset Enable each device
Reset switch each device
Up to 128K Memory each device
Up to 16K SRAM each device
Up to 4 EEPROM each device
32 IO pins each device, plus Aref, brought to edge connector with Ground pin each device.
Add jumpers from headers to have Serial, SPI, I2C comm's between the devices - Set up Real Dual-Core Processing!
Imagine the possibilities: 12 channels of PWM - 16 channels of Analog inputs - 4 serial ports - 2 SPI ports - 2 I2C ports - what could you make?
All in a handy 80x100mm card with removable processors in case they get damaged.
These screen shots hardly do the design justice!
(okay, maybe I should get to bed sooner ...)
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.

Aviator

Awsome!


However, I fail to see the purpose of the post. Are you selling this board? Are you about to produce it? What do you want the community to do?

Aviator

liuzengqiang

tow mcus sharing one crystal? I have npt seen this before.
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

retrolefty


Awsome!


However, I fail to see the purpose of the post. Are you selling this board? Are you about to produce it? What do you want the community to do?

Aviator


CrossRoads is just showing off his circuit layout skills, while waiting for the pending hurricane.  ;)

CrossRoads

Well, I thought I'd build one up & see how it goes!

"The pins XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which
can be configured for use as an On-chip Oscillator, as shown in Figure 8-2 on page 32. Either a
quartz crystal or a ceramic resonator may be used."

"This Crystal Oscillator is a full swing oscillator, with rail-to-rail swing on the XTAL2 output. This is
useful for driving other clock inputs and in noisy environments. The current consumption is
higher than the "Low Power Crystal Oscillator" on page 33. Note that the Full Swing Crystal
Oscillator will only operate for Vcc = 2.7 - 5.5 volts."

I got the idea from an older post where 2 '168s shared a crystal. Gonna put a couple on a breadboard and try it before I order boards to make sure.

I am really happy with the layout. Minimal # of vias, .016-.024-.032" traces throughout, .05" for power.   Good user configurability too.
I didn't put an FTDI chip on the board, just the header to connect one to each device.
I figure with CP2102 based  USB to serial adapters available for just $2-3 dollars, why put a hard to solder $4.50 FTDI chip on the board that is only used for downloading sketches? Plug on one, or connect via a header cable, unplug & go!

And having some fun, as Lefty recognized 8)
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.

liuzengqiang

So one mcu drives the crystal to oscillate and the other receives the oscillation? I saw the solder jumper this time.
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

JoeO

Nice design Bob:  3 questions

What about some screw holes for mounting?

Are the "top" and "bottom" rows of I/O pins on 0.1 inch centers so that it can be inserted into a proto Board?
  If so, Can you put some ground pins inline so that they can be brought onto the proto board?

Thanks

retrolefty

Quote
I didn't put an FTDI chip on the board, just the header to connect one to each device.
I figure with CP2102 based  USB to serial adapters available for just $2-3 dollars, why put a hard to solder $4.50 FTDI chip on the board that is only used for downloading sketches? Plug on one, or connect via a header cable, unplug & go!


I sure agree with that. With the avaliblity of these super cheap USB TTL serial cable modules, why would anyone want to waste their valuble board space and added costs to place a USB serial chip or any kind onto their standalone PCB? That space if avalible could be put to much better use IMHO. Just put the needed pins to a header and move on to something more cool.  ;)

Lefty

CrossRoads

Ok,
Screw holes added on 0.1" grid. Got the 2 rows of edge connectors on 0.1" grid. Added 4 ground hole pads near the end of each row of connectors.
Tweaked traces to let ground plane fill in more. Cleaned up nameplacements.
Any other suggestions? I'm all ears.
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.

Coding Badly


These dual processor boards have me wondering if anyone uses AVR processors in applications that need symmetric redundancy.

CrossRoads

Not that I am aware - but I am betting that having one processor do high speed data capture and writing to memory and having the 2nd move it to an SD card will be a lot easier!
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.

retrolefty

#11
Aug 28, 2011, 03:18 am Last Edit: Aug 28, 2011, 03:23 am by retrolefty Reason: 1


These dual processor boards have me wondering if anyone uses AVR processors in applications that need symmetric redundancy.



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

Lefty


JoeO

Is there enough room to use solder tail sockets on the 232s ?

CrossRoads

I believe so. Take a look:
http://www.crossroadsfencing.com/DualATMega1284.brd
right-click, save-target-as, rename to .brd
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.

JoeO


I believe so. Take a look:
http://www.crossroadsfencing.com/DualATMega1284.brd
right-click, save-target-as, rename to .brd

Bob: I can't tell by looking.  You board layout and EAGLE skills far exceed mine. 
I am just looking at your design as a user.  The question I ask myself is "what features would I want".  Having the option to socket all of the chips is one of them.

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