Mega4809 at DigiKey

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Just got an announcement from DigiKey.

 

ATmega4809 98 units on hand, 1.55 USD for single item

 

ATmega4809 Xplained Pro 5 on hand, 38.00 USD single item

 

Jim

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

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Seems a great chip EXCEPT!! it can't run form a "normal" crystal at anything above 32KHz and we know how accurate those types of clocks are(!).

 

Why or why, with all the junk available on the chip, they could not provide a standard crystal oscillator mode? But what do I care? cheeky

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

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js wrote:

Seems a great chip EXCEPT!! it can't run form a "normal" crystal at anything above 32KHz and we know how accurate those types of clocks are(!).

 

Why or why, with all the junk available on the chip, they could not provide a standard crystal oscillator mode? But what do I care? cheeky

 

Exactly..   

 

One wonders if the fact Microchip makes Oscillators, but does not make Crystals, has anything to do with this ?

 

Problem there is multiple..

* Crystals are still much cheaper than oscillators

* Microchip oscillators are not available in 5V models (in fact, few do 5V oscillators)

* If you want to use the very accurate low cost GPS clipped-sine TCXO sources, those need an amplifier... which the Xtal stage nicely provided.

   There even is scope for MCUs to include a self-biasing 1 pin EXTCLK choice, to manage these low cost Clipped Sine Oscillators.

 

End outcome is a highly flexible microcontrolller, that is suddenly rather less flexible...

 

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js wrote:
...  they could not provide a standard crystal oscillator mode?
Internal RC oscillators are more robust than a crystal and megaAVR 0-series has an impressive dt-CLCL of 20% max (change in clock period, clock cycle to clock cycle)

At a constant Vdd, mega4809's 20MHz RC frequency varies by temperature by 1% typical; a USB UART ideally should sync to the USB SOF so that end of the communication link is better than 1%.

But, the clock calibration app note hasn't been updated for megaAVR 0-series.

In the meantime, some USB UART can provide a clock from a fractional BRG or its crystal oscillator.

Microchip Technology

Application Notes

AN_2555 AVR053: Calibration of the internal RC oscillator

http://www.microchip.com//wwwAppNotes/AppNotes.aspx?appnote=en591393

(PDF)

1.6. RC Oscillator Revision History

(version 5.0 (PicoPower), 8.0MHz)

5. Revision History

09/2016

Microchip

Microchip

Atmel Studio

Programming Dialog

Oscillator Calibration

http://www.microchip.com/webdoc/GUID-ECD8A826-B1DA-44FC-BE0B-5A53418A47BD/index.html?GUID-6D2437A8-62FE-4621-843C-E2B7FCC36486

https://www.microchip.com/wwwproducts/en/ATMEGA4809

https://www.exar.com/products/interface/uarts/usb-uarts (Exar USB UARTs, parametric search)

https://www.olimex.com/Products/Breadboarding/BB-CH340T/resources/CH340DS1.PDF (USB UART CH340, search for CKO)

 

P.S.

Exar USB UARTs do not have 5V I/O.

Microchip USB UART MCP2221A has 5V I/O when USB VBUS powered, 13mA typ with USB suspend per USB spec (0.5mA), and a 2500ppm (0.25%) max clock output at :

  • 24MHz
  • 12MHz default
  • 6MHz
  • 3MHz
  • 1.5MHz
  • 750KHz
  • 375KHz

http://www.microchip.com/wwwproducts/en/MCP2221A

 

Edit: MCP2221A

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Thu. May 17, 2018 - 04:04 AM
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Who-me wrote:
But what do I care?
You care more than I do. After you go through the pain of setting up a decent ARM developing environment (almost there) I can not imagine any reason for looking back.

Though I will probably keep using some AVR's for the existing (hobby) projects I have and for projects with similar functionality for which my own libraries fit.

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

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You care more than I do

I don't think so. Remember I'm semi retired so all I do is for fun, if I can't do it with a "normal" AVR, maybe Xmega (preferably with AS4.18 and assembler..... devil but I'll lower myself to C and AS7.....) then I don't do it.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I guess that the main problem is/was that the new/cheap production line don't work with full swing OSC. (see 328PB!)

 

So this is for me a hobby controller !

 

And the fact that the missing memory mapping of registers do that a lot of my ASM code have to be rewritten/restructured make me stay

(same reason I never went for xmegas.)  

 

And I guess that Microchip better update a lot of tut's for the new chips to fly :(

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Who-me wrote:

* Crystals are still much cheaper than oscillators

 

Much cheaper? I pay around 0.25 for a crystal in small quantities (GBP/EUR/USD, it doesn't really matter). I can get an oscillator for around 0.50. OK, so in percentage terms that's double, but in cash terms it's not that much more.

"This forum helps those that help themselves."

"How have you proved that your chip is running at xxMHz?" - Me

"If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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 I can get an oscillator for around 0.50. OK

Where do you get a 5V 20MHz version for that price? (<10 at the time) 

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Mouser at 0.72 for 10+...

 

https://www.mouser.co.uk/Product...

"This forum helps those that help themselves."

"How have you proved that your chip is running at xxMHz?" - Me

"If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Did a simple search on Octopart for 20MHz oscillators.

https://octopart.com/search?q=20MHz%20oscillator&start=0&sort=median_price_1000&sort-dir=asc

On the first page I found one from Abracom

https://datasheet.octopart.com/ASFLM1-20.000MHZ-L-C-T-Abracon-datasheet-10050101.pdf

<10 prices are not listed, but 1000+ prices are 12ct or 10ct @ "Verical" and "Newark".

 

On another oscillator I clicked through to newark:

http://www.newark.com/txc/8w-20-000mbc-t/oscillator-20mhz-2-5-x-2mm-cmos/dp/29X6525?CMP=AFC-OP

I do not really know what to think of that.

They seem to cost USD2.08 (10 up) but also at the 12 ct price octopart suggested.

Weird. True, or clickbait?

Edit:

Oops, that one is only 3V3.

But you can find so many, from different places via octopart. Give it a try.

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

Last Edited: Wed. May 16, 2018 - 09:03 PM
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The 12c price is for China......

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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js wrote:

The 12c price is for China......

 

yes, and also stock clearance prices can distort the disti searches.

 

If you want to match the Vcc range of an AVR, the choices are few...

KC5032A20.0000CMGE00 Kyocera International  XO 20.000MHZ CMOS SMD 1,355 - Immediate $1.63 /1  CMOS 1.6 V ~ 5.5 V ±50ppm -40°C ~ 85°C 7mA

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I rather despise these split datasheets...they start out good then coagulate until they are no longer good...then after awhile you have to figure out which "datasheet pieces" belong with which chip.

 

This is the manual for mega-0 parts (except for the mega8467, and the adc section of the mega6428)  Only the mega2428 supports the wifi peripheral in all modes.  

 

Just give me one datasheet for one chip!

When in the dark remember-the future looks brighter than ever.

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Who-me wrote:
* Microchip oscillators are not available in 5V models ...
could level translate to 5V; additional estimated current is about one fifth of a mega4809 at 20MHz (approx 10mA typ)

Who-me wrote:
 ... (in fact, few do 5V oscillators)
Analog Devices/Linear Technology silicon oscillators is one source; 3mA typ and 2.5% max frequency error.

 


http://www.microchip.com/design-centers/clock-and-timing/oscillators (MEMS, 1.3mA typ at 1.8V, DSC60XX)

http://www.onsemi.com/PowerSolutions/product.do?id=NLSX4378 (24Mbps, 10K passive pull-up after active pull-up)

http://www.analog.com/en/products/clock-and-timing/silicon-oscillators/ltc1799.html (LTC1799, 1kHz to 33MHz Resistor Set SOT-23 Oscillator)

 

"Dare to be naïve." - Buckminster Fuller

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ka7ehk wrote:
ATmega4809 98 units on hand, 1.55 USD for single item
Mid-August for QFN at about the same price.

http://new.microchipdirect.com/product/ATMEGA4809?keywords=ATMEGA4809-MFR

 

"Dare to be naïve." - Buckminster Fuller

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gchapman wrote:

could level translate to 5V; additional estimated current is about one fifth of a mega4809 at 20MHz (approx 10mA typ)

 

True, for even more cost, (33c/3k is more than small MCUs !) and another part on the BOM and to place....

 

gchapman wrote:

Analog Devices/Linear Technology silicon oscillators is one source; 3mA typ and 2.5% max frequency error.

http://www.analog.com/en/products/clock-and-timing/silicon-oscillators/ltc1799.html (LTC1799, 1kHz to 33MHz Resistor Set SOT-23 Oscillator)

 

I'll admit I'd forgotten about those, given the poor precision and very high price.... LTC1799CS5#TR   2500 $2.670 - does anyone buy those today ?

 

 

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What is the problem with calibrating from a 32KHz crystal? Or, does that not work with this family? #5 suggests that it does work.

 

Jim

 

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

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ka7ehk wrote:

What is the problem with calibrating from a 32KHz crystal? Or, does that not work with this family? #5 suggests that it does work.

 

Nothing wrong with calibration, as far as that goes...

The step-granularity is usually the limiting factor, plus the jitter present in RC Oscillators as well.

 

So you get nothing like a Crystal in final stability.

 

For many low-spec apps, that may be 'good enough' but it means the MCU cannot be (as easily) used for higher spec designs, as earlier MCU models.

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ka7ehk wrote:
Or, does that not work with this family?
'that' being AVR053 and Atmel-ICE generates a calibration clock over ISP or JTAG.

For megaAVR 0-series, Atmel-ICE can still generate the calibration clock but calibration complete is TBD.

http://ww1.microchip.com/downloads/en/AppNotes/Atmel-2555-Internal-RC-Oscillator-Calibration-for-tinyAVR-and-megaAVR-Devices_ApplicationNote_AVR053.pdf

(page 7)

2.1. Calibration Protocol

(third paragraph)

The overall concept is that the programming tool generates the calibration clock (C-clock), and the device uses this as a reference to calibrate its internal RC oscillator. When the device has completed the calibration it signals “OK” to the programming tool on the (ISP MISO or JTAG TDO)

...

 

"Dare to be naïve." - Buckminster Fuller

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Ahh, a little different from the "classic" calibration.

 

Thanks

Jim

 

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

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One 1M resistor and one 74HC1GU04 one-gate sot23-5 (or even smaller sc88) 5pin unbuffered inverter. That's all it takes. Or if you want to play with power/swing levels you can use an additional series resistor (220R...2K2) and play with the 1M resistor (I've seen values from 220K to 4M7 - usually 2M2).

This is what I'm using with ATmega88PB in lots of designs. In fact I have two designs types:

- one for a 3pin rezonator (with integrated capacitors) with 1M resistor.

- one for a crystal with 1M8 resistor and a series 1K resistor (with external capacitors of course, 27pF).

Works like a charm.

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rammon wrote:

One 1M resistor and one 74HC1GU04 one-gate sot23-5 (or even smaller sc88) 5pin unbuffered inverter. That's all it takes. Or if you want to play with power/swing levels you can use an additional series resistor (220R...2K2) and play with the 1M resistor (I've seen values from 220K to 4M7 - usually 2M2).

This is what I'm using with ATmega88PB in lots of designs. In fact I have two designs types:

- one for a 3pin rezonator (with integrated capacitors) with 1M resistor.

- one for a crystal with 1M8 resistor and a series 1K resistor (with external capacitors of course, 27pF).

Works like a charm.

 

Sure, there are even parts like 74LVC1GX04, that are designed for Oscillator use. Also useful are the 74AHC1G42xx series - I'm told a range of dividers are 'coming'.

The point is, if you are buying a general purpose microcontroller, you should not have to be doing these work-around dances of adding-more-parts at all :)

 

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Who-me wrote:

The point is, if you are buying a general purpose microcontroller, you should not have to be doing these work-around dances of adding-more-parts at all :)

Sure, here we can discuss:

- why putting a crystal at all? There are LOTS of micros with 1%, 1.5%, 2% over the entire temperature range already. Not Atmel's/Microchip though.

- why needing specific frequency at all? At least for UARTs when ST for example had fractional baud generators for years. Atmel/Microchip seems to realize this only lately.

And these are related only with the clocks.

In the 90s we were used to put reset generators and watchdogs externally, and that seemed normal. Not today, of course. But I still have a design in production even today in 2018, using an old romless 8051 with external everything... Working just great for that application smiley

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rammon wrote:

There are LOTS of micros with 1%, 1.5%, 2% over the entire temperature range already. Not Atmel's/Microchip though.

 

If I read the 4809 datasheet correctly then the key points are...

 

factory calibration of 16/20MHz is +/-0.75%

calibration step size is 0.75%

drift over normal operating range is +/-1.5%

total error over full operating range is +/-3%

 

Those all compare quite well with other 8-bit general purpose micros

"This forum helps those that help themselves."

"How have you proved that your chip is running at xxMHz?" - Me

"If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Brian Fairchild wrote:

rammon wrote:

There are LOTS of micros with 1%, 1.5%, 2% over the entire temperature range already. Not Atmel's/Microchip though.

 

If I read the 4809 datasheet correctly then the key points are...

 

factory calibration of 16/20MHz is +/-0.75%

calibration step size is 0.75%

drift over normal operating range is +/-1.5%

total error over full operating range is +/-3%

 

Those all compare quite well with other 8-bit general purpose micros

Not bad. But. For me "full operating (temperature) range" is the magic phrase. Unusable if not within +/-2%. For uart applications, of course.

That's not the point. I do what I have to do. Using external HCU gate for oscillator on the PB parts. Not complaining. (Remember, PB parts do have internal crystal osc. but the chip is very very susceptible to noise with it). I compared the ATmega88P with ATmega88PB prices.... Decided that a small additional single-gate part woths the effort.

Maybe Microchip needs to make an application note about using external oscillators for their chips. And maybe also explain why they don't have an internal one for the 0/1-series. I admit this is a bit disturbing because everyone is used to have one... 

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3V3 oscillator, 5V AVR

 

It's not pretty but it might work (might need a cap across the lower diode)

 

"This forum helps those that help themselves."

"How have you proved that your chip is running at xxMHz?" - Me

"If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Or even...

 

"This forum helps those that help themselves."

"How have you proved that your chip is running at xxMHz?" - Me

"If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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There's more than enough swing out of a 3V3 oscillator, you just need to centre it between Vil and Vih

"This forum helps those that help themselves."

"How have you proved that your chip is running at xxMHz?" - Me

"If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Maybe build a clock generator from discrete parts? I was reading this discussion: http://www.chatzones.co.uk/discu...

But it seems they are somewhat unreliable and the inverter gates used need to be chosen carefully.

 

Edit: Apparently this circuit is called Pierce Oscillator. Always learning.

Last Edited: Thu. May 17, 2018 - 10:46 AM
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ka7ehk wrote:
ATmega4809 Xplained Pro 5 on hand, 38.00 USD single item
Just out of interest - has anyone looked at the schematic for that - how do they clock the chip there?

 

EDIT: OK, so answering my own question...

 

If those ppm figures are to be believed that's pretty good isn't it?

 

PS for the curious the complete schematic is at: http://ww1.microchip.com/downloa...

Last Edited: Thu. May 17, 2018 - 10:49 AM
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It has already been discussed, I think, that you can use a 32kHz crystal like that to calibrate the internal oscillator, however the step size of the calibration is 0.75% (7500 ppm) so you are limited to half that accuracy in a worst case scenario (i.e. aprox. 4000 ppm).

Still, this is better than the TinyAVR-1 that have a step size of 1.5% (15000 ppm).

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ka7ehk wrote:
What is the problem with calibrating from a 32KHz crystal?
That is linked to mega4808.

Microchip Technology Inc

Microchip Technology

Application Notes

AN_8002 AVR055: Using a 32kHz XTAL for run-time calibration of the internal RC

http://www.microchip.com/wwwappnotes/appnotes.aspx?appnote=en591195

from AVR053 :

(page 1)

In some systems it may be necessary to perform run-time calibration of the oscillator using an external crystal. This is covered in the “AVR055: Using a 32kHz XTAL for run-time calibration of the internal RC” application note.

A 32KHz MEMS oscillator is accurate (100ppm) "enough" :

https://abracon.com/products.php?search=osc&type=MEMS&subtype=kHz%20SMD

 

"Dare to be naïve." - Buckminster Fuller

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El Tangas wrote:

Maybe build a clock generator from discrete parts? I was reading this discussion: http://www.chatzones.co.uk/discu...

But it seems they are somewhat unreliable and the inverter gates used need to be chosen carefully.

 

Edit: Apparently this circuit is called Pierce Oscillator. Always learning.

Surprising no one there mentions a 74HCU04 (mentioned above), or these days, something like a SOT353 74AHC1GU04SE

 

That U is vitally important, and means Unbuffered, so is a linear inverter. (the same Linear Inverter as they used to put inside these MCUs, until someone decided not to... )

The 74LS/74HC04 parts have far too much gain to be reliable oscillators, no surprise they are reporting unreliable ....

 

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clawson wrote:

If those ppm figures are to be believed that's pretty good isn't it?

'pretty good' is relative... :)

 

That's certainly better than any RC oscillator, but the 32KHz crystals have a parabolic tempco curve & the  20ppm spec is only room temp tolerance.

 

Image result for 32khz crystal temperature curve

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Brian Fairchild wrote:

There's more than enough swing out of a 3V3 oscillator, you just need to centre it between Vil and Vih

 

Sounds good, they could even do a simple self-biasing pin, like is found on the Sig_in pin of HC4046 - that would accept Clipped Sine, and oscillators down to 1.8V

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Who-me wrote:

El Tangas wrote:

Maybe build a clock generator from discrete parts? I was reading this discussion: http://www.chatzones.co.uk/discu...

But it seems they are somewhat unreliable and the inverter gates used need to be chosen carefully.

 

Edit: Apparently this circuit is called Pierce Oscillator. Always learning.

Surprising no one there mentions a 74HCU04 (mentioned above), or these days, something like a SOT353 74AHC1GU04SE

 

That U is vitally important, and means Unbuffered, so is a linear inverter. (the same Linear Inverter as they used to put inside these MCUs, until someone decided not to... )

The 74LS/74HC04 parts have far too much gain to be reliable oscillators, no surprise they are reporting unreliable ....

 

Yes, the U (unbuffered) is the key point. For normal gates they even usually show the symbol with three gates in series in the datasheets :) . 

The price difference for example, between ATmega88P and ATmega88PB is a full dollar! I decided to use PB with an HCU gate. For over 1000 boards/year I think it's woth the effort.