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ET-AVR Stamp
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spamiam



Joined: 13 Nov 2005
Posts: 689
Posted: 04 July 2006, 23:08 PM    Post subject: Reply with quote
dkinzer wrote:
When it is available, the mega1281 would permit as much as 7.5K User RAM.


Of course there is also the 256K version now. But from what I understand, addressing all the address space at once is not supported with the (most common) free C compiler. Since I have no need for THAT much space, I have not tried it.

BUT, I did design, on paper, a DIL "stamp" with an ATMega128, as you may remember. If you ever have any interest in such a thing (called a ZX-128?) let me know and I will give you the designs I have. With yo9ur experience, I am sure it would be trivial for you to come up with something similar but better without my stuff!

-Tony
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stevech



Joined: 23 Feb 2006
Posts: 688
Posted: 05 July 2006, 2:43 AM    Post subject: Reply with quote
Putting the user program p-code in flash would be neat I think - eliminating the need for the serial EEPROM and freeing up some port bits.
----------------------

Having run a couple of programs on this board now, I'm befuddled that the MOSI/MISO signals for the ISP are now on port E and share the same bits as USART0's TX and RX. So my RS232 level shifter's TX data seemingly would conflict in terms of bucking 1's. This would be true for all mega128's. The MOSI/MISO bits aren't on Port B in these chips.
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mikep



Joined: 24 Sep 2005
Posts: 771
Location: Austin, TX
Posted: 05 July 2006, 3:36 AM    Post subject: Reply with quote
dkinzer wrote:
The RAM space available for user programs in a mega128-based ZX would likely be 3.5K (including the string heap). When it is available, the mega1281 would permit as much as 7.5K User RAM.

Actually I was thinking that you could use an external SRAM connected to ports A and C that will give you up to 60K (or 64K) of RAM.

On a ATMega128, Port A's functionality is done by Port F and Port C's functionality is mostly done by Port E. Unfortunately Atmel couldn't resist renaming and moving around all of the I/O pins.

It does mean that we can still get all of the I/O we like on a ZX-24/ZX-44 plus 60K of RAM. It's like an old BX-01 on steriods.

Cubloc have already proven that you can fit a MLF ATmega128 in a 24-pin stamp module. All that is left now a little bit of PCB design and a few lines of code Smile
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spamiam



Joined: 13 Nov 2005
Posts: 689
Posted: 05 July 2006, 14:07 PM    Post subject: Reply with quote
mikep wrote:
All that is left now a little bit of PCB design and a few lines of code Smile


YES! Unfortunately a 4 or 6 layer board probably would be necessary, and I can only make 2 layer boards because I am using the free version of Eagle. I think that the cost of one that would do this would cost $600 (?). While I usually do not end up using the autorouter function, I DO make use of it in the early stages to see what component layout might be most efficient. 4+ layers proably makes this less of an issue and one can keep related components very close together.

It does sound like a decent idea. I do not know how many people have a sufficiently large application that a regular ZX will not fit. So far, I have not run out of space on my ZX-24, but I do not use it for the most demanding tasks. I just use a regular AVR programmed in C and all that.

-Tony
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DH*
Guest
Posted: 05 July 2006, 14:28 PM    Post subject: Reply with quote
The complexity of designing a multilayer 24-pin board is what makes me think porting the ZX system to the $20 ETT board is attractive, especially if it could be ordered with a different XTAL Adding external SPI EEPROM for data and RS232 drivers is not that difficult. In my application, the drivers are needed with the ZX-24 or ZX-40, anyway.

For me, a ZX-24 built with the ST M95512 (or ZX-40 using it) would be more than sufficient. Unfortunately, the minimum order for the ST M95512 is about $6K.

What are the dimensions of the ETT AVR-Stamp board? It appears to be just over 2.5" long. How wide?

What would be even more exciting would be ZBasic on a PIC (e.g. 16F877) that comes in a PLCC package.
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stevech



Joined: 23 Feb 2006
Posts: 688
Posted: 05 July 2006, 16:38 PM    Post subject: Reply with quote
The ETT board, IMO, is what it is. I wouldn't think it's relevant to anything greater; it's just a simple PCB with a mega128 and no support devices.

PIC - barf! I did PICs way back and grew weary of the paged memory architecture. No thanks. That was in the burn-crash-UV/erase-reburn days. I also think that Microchip's long term competitive viability versus the biggies is suspect. Atmel is a much more substantial company, though the AVRs are a small portion of their product base. And Atmel struggles to compete among the biggies.
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DH*
Guest
Posted: 05 July 2006, 17:08 PM    Post subject: Reply with quote
stevech wrote:
The ETT board, IMO, is what it is. I wouldn't think it's relevant to anything greater; it's just a simple PCB with a mega128 and no support devices.

I understand that completely and do not at all mind plugging it into another board that has the other things needed. Can you answer my question about the size of the board?
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mikep



Joined: 24 Sep 2005
Posts: 771
Location: Austin, TX
Posted: 05 July 2006, 17:50 PM    Post subject: Re: ET-AVR Stamp Reply with quote
mikep wrote:
Apparently this board is actually made by a Thai company and here is the only documentation I could find.

I posted this documentation link earlier. The PDF spec sheet shows that the board is 1.653543 inches wide (or 4.2 cm).
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DH*
Guest
Posted: 05 July 2006, 18:00 PM    Post subject: Re: ET-AVR Stamp Reply with quote
mikep wrote:
I posted this documentation link earlier. The PDF spec sheet shows that the board is 1.653543 inches wide (or 4.2 cm).
I looked at that - I just gave up before seeing the dimensions. Thanks.
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mikep



Joined: 24 Sep 2005
Posts: 771
Location: Austin, TX
Posted: 06 July 2006, 7:26 AM    Post subject: Reply with quote
dhouston wrote:
For me, a ZX-24 built with the ST M95512 (or ZX-40 using it) would be more than sufficient. Unfortunately, the minimum order for the ST M95512 is about $6K
I'm curious to know if you exceeded or are close to exceeding 32K bytes of ZBasic program memory. I would be surprised because ZBasic gives you a 50% reduction in size which still gives quite a bit of breathing room even if half of the 32K is used by data.

Also you might want to investigate the 25HP512 (64Kx 8 EEPROM) which is more readily available in small quantities although I have noticed a slow price increase over the last year or so.
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DH*
Guest
Posted: 06 July 2006, 10:47 AM    Post subject: Reply with quote
mikep wrote:
I'm curious to know if you exceeded or are close to exceeding 32K bytes of ZBasic program memory.
It's not program space alone which concerns me. I need a lot of data space as well.
Quote:
Also you might want to investigate the 25HP512 (64Kx 8 EEPROM) which is more readily available in small quantities although I have noticed a slow price increase over the last year or so.
I'm well aware of the 25HP512 but its price is prohibitive (this is a DIY project and users will buy components in QTY 1 - $11.01 @ Digikey), Digikey appears to be dropping it from stock, and it does not have a byte write mode. Microchip's 128K x 8 EEPROM (25LC1024) costs less and has byte write. Even wasting half of it is cheaper than the 25HP512 although it is also hard to find.
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spamiam



Joined: 13 Nov 2005
Posts: 689
Posted: 06 July 2006, 16:44 PM    Post subject: Re: ET-AVR Stamp Reply with quote
dhouston wrote:
mikep wrote:
I posted this documentation link earlier. The PDF spec sheet shows that the board is 1.653543 inches wide (or 4.2 cm).
I looked at that - I just gave up before seeing the dimensions. Thanks.


At that width, it is not really breadboard-able. The standard breadboards are a maximum of 5 holes on the left, 5 on the right, and one skipped in the middle. Total of 1.1", but to be useful you need at least one free hole on either side. Therefore the widest useful dual in-line package is 0.9" wide.

I was able (just) to cram an ATMega128, the crystal, clock caps, Analog voltage inductor and ISP or JTAG connector as well as a FRAM on the one 2-layer board. It has 54 pins (as I remember) with PORT G being a separate header on top, or a longer board with all the free pins of the AVR existing in the DIL footprint..

The design was intended to be stackable and I found a source of pin/socket headers for that purpose.

The stackable boards could supply any number of different functions. I have SPI SD/MMC, RTC/FRAM, I/O designed. In principle, the CPU boards can be stacked to allow multiprocessing and any interprocess communication you want.

I did not take it to the next step of real world testing mainly because I was apprehensive about soldering the 64 pin AVR package.

But, I will be soldering a different device with a similar pitch and if it goes well, I might proceed with development further. It looks as if the CPU board would not be CHEAP, but probably could sell for $40-60 and have some profit.

If anyone is interested in my designs, let me know. I am not planning on commercially producing them.

-Tony
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stevech



Joined: 23 Feb 2006
Posts: 688
Posted: 07 July 2006, 2:25 AM    Post subject: Reply with quote
another far-east suite of AVR products

http://www.ere.co.th
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