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electronic.designer
PostPosted: Feb 11, 2011 - 12:08 PM
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Hi all,

I have spent hundreds of hours studying XMEGA and I did several tests on this family and found tens of errors in Atmel datasheets and app notes.
But as I see, AVRFreaks members are not so interested on XMEGA.
The question is why?

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angelu
PostPosted: Feb 11, 2011 - 01:41 PM
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I don't like they split the data sheet in two: one describing a family, the other for a specific part. I always don't know in which one I will find what I want to know (register names, addresses etc), so I have almost always to look in both of them. Maybe it is only me.

The old stile I like, everything in one document.

George.

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leon_heller
PostPosted: Feb 11, 2011 - 02:07 PM
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It's not popular with people here because of the hardware bugs and the complexity of the device, compared with the AVR.

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jgmdesign
PostPosted: Feb 11, 2011 - 03:11 PM
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That is why the devices should be called compleXMEGAS then? :lol

Jim

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theusch
PostPosted: Feb 11, 2011 - 04:00 PM
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Quote:

It's not popular with people here because of the hardware bugs and the complexity of the device, compared with the AVR.

I think it might have caught on more, or at least faster, if:
-- there hadn't been the >>years<< delay until parts became somewhat available
-- the extensive errata list, that did not get cleaned up over a number of silicon revisions

Complexity? Plain-vanilla stuff isn't too much more than the AVR, IMO. But you have a lot more features/flexibility. So you have to specify, and configure the I/O registers to use the features.

I 9and others) were very excited when the announcement came out. Leon has participated in many discussions of "better" micros than the classic AVR. I saw the Xmega as an intermediate step between the classic AVR and moving to ARM or other totally different family.

Many of the "complex" features are ARM-like. At least akin to the features in the SAM7S ARM7TDMI I was considering before the Cortex took off. This is the crux of the problem, IMO: these Xmega features were announced, but by the time they came to [buggy and spotty availability] fruition, a couple of generations of Cortex are on the scene. The window was missed, at least for me. Perhaps I might nibble if the devices become stable and with a manageable errata list.

A short list: 12-bit fast[er] ADC; couple of DAC channels; DMA; advanced interrupt controller; enhanced ports; more/more flexible timers and USARTs. Then compare to Atmel's own SAM7S models--the subsystems mentioned look substantially the same. So why is e.g. ADC so crappy over several silicon revs, when Atmel already had it stable and in production? Same with the flash read speed problems.

The "family" doc plus the model-specific datasheet is very common nowadays; I wouldn't criticize that.
 
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leon_heller
PostPosted: Feb 11, 2011 - 04:07 PM
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They could have done quite well, but Atmel seems to have given up on them.

I actually bought a few chips and was thinking of using them, but discretion being the better part of valour, I abandoned the idea.

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stevech
PostPosted: Feb 11, 2011 - 04:34 PM
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XMEGA and PIC32 make no sense to me, given the plethora of suppliers for ARM7/9/Cortex.
 
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leon_heller
PostPosted: Feb 11, 2011 - 04:39 PM
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The MIPS processor used in the PIC32 has several advantages over the ARM. They are pin-compatible with the larger 16-bit PICs, and use the same peripherals, making it easy to increase the performance of a system without a hardware redesign.

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DocJC
PostPosted: Feb 11, 2011 - 05:12 PM
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Quote:
AVRFreaks members are not so interested on XMEGA.

It could be, also, that as is often the case the complainers are speaking out, and very visible & vocal, while those that have adopted it are simply getting on with what they are doing.

I happen to like the Xmega, and it is my chip-of-choice these days, unless I am using a Tiny as a front end processor. That said for a recent project that I had anticipated using an Xmega for I ended up using a Mega with its trouble free ADC instead of the Xmega and an external ADC.

But I buy uCs 10 at a time, not 10K at a time, so my impact on the series' long term market share and success is minimal.

JC
 
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ArnoldB
PostPosted: Feb 11, 2011 - 05:14 PM
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electronic.designer wrote:
But as I see, AVRFreaks members are not so interested on XMEGA.
The question is why?
Oh, people were excited about it - until they found out the truth.

It started with a press release in February 2008. There some Atmel marketing guy claimed something like "immediate available". However, mere mortals couldn't get one for a year or longer. In the meantime Atmel managed to *cough* convince *cough* a trade rag to declare this vapourware "Product of the year". Then Atmel came out with an eval board, the Xplain. Only that you couldn't buy it, you had to take part in some exclusive seminar.

People were literally begging Atmel to sell them an eval board or just an Xmega. Atmel didn't care. In fact, Atmel didn't care to communicate at all about the Xmega, except listing more and more Xmega variants on their website, non being available.

And when people could finally get some Xmegas it turned out they were badly broken (AFAIR rev. G of the 128A1). Then the next revision (AFAIK rev. H) came out, still badly broken.

The Errata list is growing ever since. And IMHO it is still incomplete. E.g. I think the fact that a good bunch of Xmegas came (or still come?) with no calibration data in the calibration row isn't mentioned.

I can say that whatever part of the Xmega I touched, it turned out to be broken after I spent a lot of time to get it working. Until I gave up on the Xmega.

And of course, Atmel isn't communicating. People are stuck with the broken revision, and no word or information when, if at all, Atmel intends to fix some issues.

Also, it took a long time until Atmel added Xmega programming support to their garden-variety programmers. The Dragon's PDI support is still limited to a few Xmega models. And Atmel didn't and doesn't communicate about that.

When people here asked for an Xmega forum, they didn't get one. What we got was a useless security products forum. Atmel quickly abandoned that forum, when it didn't result in the intended burst of sales (hint: What good is a forum for products one can't buy from normal distributors?).

This ridiculous ASF library is also not helping. For some time people were literally begging Atmel to release the complete source code of the Xplain software. AFAIK it still isn't available. Instead we got a strange "xplain software framework 1.0", and later the ASF.

There is probably more that Atmel did wrong. It is a kind of textbook case of what not to do. It is not that people hate the Xmega. It is Atmel hating small-fish developers and don't giving a ...

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js
PostPosted: Feb 11, 2011 - 09:05 PM
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I would have started to use some if they came in pin compatible pinout with some Mega chips ie drop 1 into an exiting boards. But then they don't work at 5V so it's a complete redesign, more stock to keep etc.

I havent't needed the power of anything more than a mega running at 1/3 of maximum speed yet, but I could have used the "better" ADC and definetely more serial ports it offers. Otherwise bahhh humbug... Laughing

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theusch
PostPosted: Feb 11, 2011 - 09:20 PM
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Quote:

I havent't needed the power of anything more than a mega running at 1/3 of maximum speed yet, but I could have used the "better" ADC and definetely more serial ports it offers. Otherwise bahhh humbug...

My apps are nearly all like yours, js. Rarely run out of gas running at a modest (for AVR) clock rate.

But some of the features of the Xmega would allow me to tackle apps that I wouldn't do with a vanilla AVR. Lots of timers with full features such as ICP. DMA for fast logging and advanced waveform generation. Quadrature support.

And the last brings me to an app for a customer that I decided not to tackle. Four simultaneous quadrature streams that must be reported and synchronized. From my prior work, I'd have to have an AVR on each stream, and a fifth as the coordinator. A single Xmega could handle this nicely.
 
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angelu
PostPosted: Feb 11, 2011 - 09:27 PM
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It would have been great to have USB aside eight UARTs in devices with 128 - 256k of flash, but they added USB for mega with 8k.

George.

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ganzziani
PostPosted: Feb 12, 2011 - 12:08 AM
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I do like the XMEGA. Despite the bad marketing, the microcontroller itself is very nice. The errata might be long, but most of the bugs don't affect my applications, or I have worked around them.

There are things I wish the XMEGA had:
- 5V tolerant inputs
- USB

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electronic.designer
PostPosted: Feb 12, 2011 - 09:15 AM
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Thanks for replies.
Aren't these silicon bugs and erratas normal for a new family? And what is the typical time for modifying such bugs?

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leon_heller
PostPosted: Feb 12, 2011 - 09:27 AM
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Bugs like that for a new family are typical, but most of them are usually fixed before the device goes into full production. Many chips go through three or more design cycles.

It's difficult to say how long it should take to do the necessary redesign to fix bugs in silicon, but I'd have thought that it shouldn't take more than a few months with the tools that are currently available.

Microchip had similar problems with their 16-bit dsPIC family a few years ago, and announced it prematurely. They took about three years to get them working properly, but didn't actually ship any devices in that time. Silicon debugging tools were a lot less sophisticated then.

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ArnoldB
PostPosted: Feb 12, 2011 - 09:46 AM
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It is also strange that a good bunch of the bugs are rather obvious and in basic functions, but it took some while until they appeared in the datasheet.

The question is, are Atmel's test procedures so bad they don't test basics when they get a first batch of a new revision out of the factory, or did Atmel know, but releases the information piecemeal, only when they no longer can deny an issue?

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valusoft
PostPosted: Feb 12, 2011 - 10:00 AM
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ArnoldB wrote:
The question is, are Atmel's test procedures so bad they don't test basics when they get a first batch of a new revision out of the factory, or did Atmel know, but releases the information piecemeal, only when they no longer can deny an issue?
Maybe they never studied the works of W. Edwards Deming ...

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clawson
PostPosted: Feb 12, 2011 - 02:04 PM
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I'm guessing that part of it has to do with the abandonment of the Atmel owned fabs so that it may not be as easy to run engineering sample wafers down the line to iteratively correct the silicon errors?

In part some of the "problem" is making them 3V3 only which is really putting them in the ARM ball-park. Why would anyone adopt "new" silicon when you can just re-use all your ARM knowledge and tools on something more powerful that costs the same price?

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ArnoldB
PostPosted: Feb 12, 2011 - 06:49 PM
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clawson wrote:
I'm guessing that part of it has to do with the abandonment of the Atmel owned fabs


Sure. According to Deming 85% of quality issues are caused by management.

Quote:
so that it may not be as easy to run engineering sample wafers down the line to iteratively correct the silicon errors?


But Atmel could do at least the first step: To test the basic functions of a silicon revision and to properly document the issues in the errata. Instead of either not testing or keeping the bugs secrete.

Oh, by the way, the atxmega128A1 rev. H appeared around November 2008 in the A1 datasheet. Yes kids, more than two years, but Atmel didn't manage to do even one iteration to correct a few bugs (85% of quality issues are caused by management ...). Two years, no new silicon revision but an increasing Errata list, which I don't trust.

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