How can one go with Xmega when SAMD21 series is available?!

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I about to start a new project and can't make up my mind as to what MCU to use.

 

At this moment I have one project with the ATXMEGA64A3U-AU and could not be happier, the learning curve was very comfortable and I've managed to get a working proof of concept within a couple of days. The same MCU made it into production with a cost of about $3.6 per unit @ 100pcs.

 

Right now I'm evaluating an MCU for another project where an 8bit MCU is on the weak side. I was looking at the ATXMEGA64A3U-AU again, however noticed the SAMD21, which I never looked into before. The ATSAMD21J16B-MUT is also 64K with about 50 GPIO pins. At 100pcs the price is around $1.1!

 

I've looked into some sample code from ASF and it does seem "uglier" and will require harder work for adjustment, however the price difference is huge. How come this goes on like this? Isn't this killing the xmega family?

 

 

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I've been wondering the same thing myself. I've used and liked xMega for some time now, but thinking for the next project, should I ever do one again, to use SAM.

 

I don't like ASF as it's harder to use than the part itself. I found an interesting page at https://github.com/ataradov/mcu-... with sample projects for getting the sam chips going.

274,207,281-1 The largest known Mersenne Prime

Measure twice, cry, go back to the hardware store

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Thanks for the link, I'll look into it. I don't necessarily like ASF as it usually means large code and too many headers & functions to debug easily however it does create very portable code.

 

The price thing is amazing though. To put this into perspective, ARM gets to see fees for the IP - so can it be that the xmega is more expensive?

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What are your volumes? You can easily blow any per-chip savings by spending weeks and weeks learning a new chip.

'This forum helps those who help themselves.'

 

pragmatic  adjective dealing with things sensibly and realistically in a way that is based on practical rather than theoretical consideration.

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Indeed, raw chip price is only one factor of many. If it is going into a production product, then you have to amortize the development cost over the number of units you expect to sell. Plus, you need to include the losses due to delayed entry into the market (and the possibility that someone else may get there before you do); this is really hard to quantify but it is real. Some call this "cost of lost opportunity". That is, you WOULD have income sooner with the shorter development time, so that delay is a cost. 

 

In short, its (usually) not at all easy to determine "best" and it certainly includes a lot more than chip cost.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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slow_rider wrote:
How come this goes on like this?
Lack of design refresh.  Lack of process re-fab. Not wise to undercut PIC24; unwilling to commit to AVR16 (16b MCU is a sweet spot)

Lack of secure boot (ie port AVR32 UC3 FlashVault)

(I guess, I no know, I wish in one hand and ...)

slow_rider wrote:
Isn't this killing the xmega family?
No due to XMEGA niches :

  • 16b oversample-and-decimate ADC capability in XMEGA E
  • SDRAM controller in XMEGA A1U
  • Orthogonal CRC (program space, data space)
  • Increased reliability due to lack of a core voltage regulator
  • Greater likelihood to survive a Vcc over-volt
  • Greater injection current capability
  • Greater output drive current (a long-time characteristic of most AVR and PIC)
  • Reduced leakage current for some XMEGA
  • 105C models (possible for tractor cabs, steam clean wash down)

 

"Dare to be naïve." - Buckminster Fuller

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slow_rider wrote:

...

Right now I'm evaluating an MCU for another project where an 8bit MCU is on the weak side. I was looking at the ATXMEGA64A3U-AU again, however noticed the SAMD21, which I never looked into before. The ATSAMD21J16B-MUT is also 64K with about 50 GPIO pins. At 100pcs the price is around $1.1!

 

As well as SAMDxx series, there is also the 5V operation SAMC series, higher price, but more code size - keep in mind an ARM will eat more RAM and CODE than an 8 bit MCU in most control/comms tasks.

 

 

I see Microchip direct lists

ATSAMD21J16B-MUT     100+ 1.79

 

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8 bit parts are still better for power consumption, and recycling existing code... But yeah, ARM is very attractive if you don't need those things.

 

I just wish there was better support for not using vendor supplied code with ARM.

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Who-me wrote:
an ARM will eat more RAM and CODE than an 8 bit MCU in most control/comms tasks

Not sure that's entirely true, but ARMs do tend to have significantly more RAM and Flash anyhow.

 

 

mojo-chan wrote:
8 bit parts are still better for power consumption

Hmmm ... some 8-bit parts may be better - but it's not a universal certainty.

 

And many ARMs are very good at (low) power consumption these days ...

 

But, really, it just comes down to choosing the part that best fits the requirements - emotional brand attachments have no place here!

 

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awneil wrote:

mojo-chan wrote:

8 bit parts are still better for power consumption

 

 

Hmmm ... some 8-bit parts may be better - but it's not a universal certainty.

 

And many ARMs are very good at (low) power consumption these days ...

 

Compare XMEGA to SAM devices. SAM does okay on the headline figure, in the deepest sleep mode. But look at what works in that sleep mode. Look at the wake-up time. Look at power consumption when active. XMEGA is orders of magnitude better.

 

For a lot of applications this doesn't matter. But when it does matter, it's not even a competition.

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But you're talking about a specific 8-bit part.

 

My point is that you can't just say, in general, that "8 bit parts are better" - especially as some will take that to include all state-of-the-ark 8-bit clunkers.

 

But it is very true that headline figures can be unhelpful - if not misleading - for any processor.

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That was just an example. The more general point is that the ARM architecture just isn't as power efficient. It's cheaper to manufacture with bigger memories and the like, but for example to save power only a small amount of that RAM will survive the deepest sleep mode and the rest is a cheaper, less power efficient type than the SRAM commonly found in modern 8 bit parts. The clocking requirements, the multiple supply voltage requirements etc. that are typical of ARM parts, not to mention the core CPU architecture (M0+ is a 2 stage pipeline, with Von Neuman architecture and ARM's 3 operand variable length instructions) just make it impossible for them to be as power efficient as common 8 bit parts.

 

Sleep modes with ARM are a kind of after-thought, bolted on and with some severe limitations due to the architecture.

 

And of course, exceptions apply.

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So, to the question of the thread title:

How can one go with Xmega when SAMD21 series is available?!

The answer is the same as it ever has been - once considers the project requirements, and chooses the product which best fits them.

 

Price is very often an important factor - but it's no use selecting a part which is cheap, but can't do the job!

 

"Learning" is also an important cost to consider ...

 

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awneil wrote:
state-of-the-ark

 

Oh,  I hadn't heard that one before, it's being added to the phrase book :-)

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it's an old one 

 

wink

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ARMs do tend to have significantly more RAM and Flash anyhow.

...necessary for the code bloat of course.... devil

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I'm wondering about the marketability of me. I've been having that trouble lately Everybody has heard of ARM, but few would know that....

274,207,281-1 The largest known Mersenne Prime

Measure twice, cry, go back to the hardware store

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I'm wondering about the marketability of me

So how long do you have before you no longer care about that? (like me cheeky )

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Torby wrote:
I'm wondering about the marketability of me

To whom are you "marketing"?

 

If it's to job agents, they are (mostly) clueless and just do keyword matching - so it's important there to have the right keywords on your CV (resume).

 

But, if you're "marketing" direct to clients who know what they're talking about, they should be able to recognise that the vast majority of the required skills are transferable and not architecture-specific.

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Torby wrote:

I'm wondering about the marketability of me. I've been having that trouble lately Everybody has heard of ARM, but few would know that....

 

I always feel a bit nervous saying "ARM" because there is such a big range of parts and ways to use them, almost like saying "Atmel".

 

I've done Cortex M0+ from scratch, I've done Texas AM35 system-on-chip modules running Windows CE (okay, "running" is an exaggeration)... They are very different.

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mojo-chan wrote:
I always feel a bit nervous saying "ARM" because there is such a big range of parts 

Very true!

 

So, when you see Agents just say "ARM" - you know they have no clue!

 

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awneil wrote:

mojo-chan wrote:

I always feel a bit nervous saying "ARM" because there is such a big range of parts 

 

 

Very true!

 

So, when you see Agents just say "ARM" - you know they have no clue!

 

 

But unfortunately your CV often has to get past these clueless individuals before it gets to someone who knows the difference.

 

So if they're looking at two more or less identical CVs and one says "I know ARM" and the other doesn't....

Last Edited: Tue. Oct 17, 2017 - 02:42 PM
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Sad, but true - see #19

 

frown