Author Topic: How about a Digispark for the ATTiny84 series of chips?  (Read 63603 times)

n3ikq

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How about a Digispark for the ATTiny84 series of chips?
« on: June 19, 2013, 09:36:42 am »
I'm sorry if this is not posted to the right place. Hi all, first let me say I'm thrilled to find this family of products! I've been using the ATTiny 84 and 85 for a year now for various fun projects but of course have been forced to solder up the chip and give it power by scratch. While plenty easy to do, this necessary step cuts into the "fun part" of programming and using the chip! Anyway my suggestion is simple and may have already been mentioned before. The extra I/O's of the 84's would be great for a slightly larger project. Thanks!

digistump

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #1 on: June 19, 2013, 10:29:19 am »
The Digispark Pro is on my list and the Atiny84 is a top candidate - though I'm considering some of the other chips with a UART on them as well - the form factor would remain very similar with added pins on an additional side, but remaining fully compatible with the Digispark shields.

airship

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #2 on: June 28, 2013, 12:30:17 pm »
my vote = YES!  :)

gogol

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #3 on: August 02, 2013, 12:57:12 am »
What about attiny87 or attiny861 ?
Both are in the same price region, have 4 pins more (than the 84). All three (84, 87 and 861) are available in an automotive-version, the 84 goes up to 125°C and the two others up to 150°C
Furthermore the 87 has an onboard RTC, an UART, 2SPI channels and 9 vs 6 vs 4 PWM outputs.

It would fit to the concept of the digiX (which is a interface++ arduino-clone) to have an digispark interface++ clone.

I am thinking about, that some 861 or 87 could replace as well PCF8574, 74HC595, lots of other shift-registers and/or logic converters with the right software collection.
It might be the right thing for makers, when you need to have only one kind of controller in stock, flush it with the right code and it will act as an replacement for a missing component in your prototype.

regards

  gogol

« Last Edit: August 02, 2013, 01:01:11 am by gogol »

digistump

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #4 on: August 02, 2013, 03:19:48 pm »
87 and 1634 are being considered as well - but they can't produce the 16.5Mhz we need for USB communications internally - which means they'd need an external crystal making them more expensive options- the attiny84a also happens to be dirt cheap (not quite as cheap as the attiny85, but close) - that said - still weighing the pros and cons of each (I'd really enjoy having a hardware uart) - I'm working on a contract project right now that calls for the same line of processors, so that should give me some paid time to evaluate them carefully.

digistump

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #5 on: August 03, 2013, 12:27:42 am »
well let me correct myself the 84 also lacks the PLL clock needed for generating the 16.5Mhz and the 861 has it - so the 861 is looking like the only viable option without adding a crystal


Here is where it gets interesting
Price at Qty 100 (generally indicative of price at 10k as well)
861 (no ext crystal needed) - $1.72
1634 (ext crystal needed) -  $0.97
167 (16k version of 87, ext crystal needed) - $1.10
87 (ext crystal needed) - $0.97
84a (ext crystal needed, not enough pins though when one is added) - $0.72

Crystals run us about $0.35 each with loading capacitors. SO even with a crystal the 1634, 167, and 87 is a better deal.

Just for comparison the attiny85 we use now is $0.66 at Qty 100

The attiny1634 seems to be a winner here except that those prices might just be because it is new, and I do have to look at long term sourcing (or hoard them).

All that said $0.66 and one component to $1.32 ($0.97+$0.35) and three components is a big jump - I had hoped to keep the price of the Pro the same - I'm thinking with that and the extra headers and a few other changes we have up for it it will end up being a buck or two more.

Thoughts and suggestions most welcome!


cboden

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #6 on: August 03, 2013, 05:16:23 am »
I guess a buck more shouldn't be the problem. Currently i would prefer a external crystal as the internal might be not precise enough in some cases. I'm not sure if this is still the case at the ATTiny's, but for RS232  for example the "big" ATmegas always need external crystals for that reason.

If you think about the PCB design i also have another wish :-) would it be possible to rotate the power pins 90 degrees so that they are opposite to the I/O pins? This would make it easier to use it with breadboards. To be 1:1 compatible to the current shields it would be then requiered to duplicate the power pins of course. But the addional power pins opposite to the I/O pins would be very helpfull from my point of view.

gogol

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #7 on: August 03, 2013, 10:00:18 am »
One argument might me, that all but the 84 and 861 are only available in soic , qfn and other smd-packages, while the others are still available as DIP.

Pro DIP:    there is a bigger maker community behind those devices, as they can be used the "traditional way" and as well from the shop to the bread-board.
                 Thats one of the advantages of the digispark as well, that you can buy the 85 around $1 in a dip, and throw it in small projects
Pro SOIC: Advantage would be, to offer a device to makers, which was out of scope because of limited soldering equipment.
                However for that, the device needs to bring new possibilities or a much better pricing, than others.

the 1634 and 84 lacks PWM out-channels compared to the rest

for all but the 1634 is a robust high temperature automotive version available, interesting for several use cases, which could easily adapted (not necessarily that it is used in the pro)

I think (and that may be only my very own perspective), that one of the big advantages of the digispark is the community, with similar products, like e.g. littlewire, lily-tiny and core chip projects.

just a few thoughts.

I have collected some of the different core features of the five mentioned micros:
Device NameFlash (Kbytes)Pin CountMax. Operating Frequency# of Touch ChannelsMax I/O PinsUARTADC channelsTemp. SensorSRAM (Kbytes)EEPROM (Bytes)picoPowerOutput Compare channelsInput Capture ChannelsPWM Channels32kHz RTCCalibrated RC OscillatorAutomotive Version availablePrice with crystal, if needed Packages
ATtiny16341620121118212No1256Yes224YesYesNo$1.32MLF (WQFN) 20M1 20,SOIC (300mil) 20S2 20,WLCSP 12U1 12
ATtiny167162016816111Yes0.5512No319YesYesYes$1.45MLF (VQFN) 32M1-A 32,SOIC TG 20,TSSOP 6G 20
ATtiny848142061208Yes0.5512No414NoYesYes$1.07MLF (WQFN) 20M1 20,PDIP 14P3 14,SOIC (150mil) 14S1 14
ATtiny86182020816011Yes0.5512No616NoYesYes$1.72MLF (VQFN) 32M1-A 32,PDIP 20P3 20,SOIC (300mil) 20S2 20
ATtiny878201616111Yes0.5512No319YesYesYes$1.32MLF (VQFN) 32M1-A 32,SOIC TG 20,TSSOP 6G 20



regards

   gogol
« Last Edit: August 03, 2013, 10:09:27 am by gogol »

gogol

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #8 on: August 03, 2013, 11:24:31 am »
Hi,

comparing the datasheets, I wonder, how the 1634 should be able to create the 16.5MHz. Looks like, that 12MHz is the maximum.

regards

   gogol

CBcracker

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #9 on: August 05, 2013, 10:12:49 am »
1634 (ext crystal needed) -  $0.97
[...]

The attiny1634 seems to be a winner here except that those prices might just be because it is new, and I do have to look at long term sourcing (or hoard them).

I agree.  I've been looking at the 1634, and it looks like a great DIY chip too.  The ATmega8's PQFPs are cheap on the grey market (~75c), but soldering 32 .8mm pitch pins is a lot harder than 20 1.27mm SOIC pins.
You should be able to forgo the crystal and run it at 12Mhz or 12.5Mhz (in the high range of OSCCAL and it is supported by V-USB).  It has a temperature controlled clock generator (see datasheet 6.5.4
OSCTCAL0A – Oscillator Temperature Calibration Register A), so I think there's a decent chance it could be stable enough to do USB communications at 12Mhz (i.e. not the more bloated 12.5Mhz version of the v-usb code).
It also has an on-chip, low-power calibrated 32.768khz oscillator - so no need for RTC shields.

I'd also dump the on-board regulator.  When not connected to the computer it's easy to power something like the digispark from a small battery, or a cheap USB charger.

CBcracker

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #10 on: August 05, 2013, 10:20:05 am »
One argument might me, that all but the 84 and 861 are only available in soic , qfn and other smd-packages, while the others are still available as DIP.
  gogol

Small SOCI -> DIL adapters are available from a number of sources, and soldering a half-pitch 20-pin SOIC isn't that hard.


gogol

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #11 on: August 05, 2013, 12:13:17 pm »
however the adapters cost at least three times of the attiny ;-) at least when I compare the prices from my usual sources!
The discussed attinys are in the range of 1€ up to 2.5€ per single piece, the adaptors in the range from 5€ to 14€ :-(

I like just now dealing with the attiny85. I bought 10 pieces, and I just plug them into a socket of my  littlewire-driven digispark, to program them.
After that, I plug them into the breadboard for next round of testing.

With soldering adapters, that will not be so much fun.

regards

  gogol
« Last Edit: August 05, 2013, 12:19:26 pm by gogol »

CBcracker

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #12 on: August 05, 2013, 08:42:18 pm »

Crystals run us about $0.35 each with loading capacitors. SO even with a crystal the 1634, 167, and 87 is a better deal.


That seems high.  Tayda sells 16Mhz crystals for 10c (qty 1!).
http://www.taydaelectronics.com/crystals-resonators-oscilliators/crystals/16-000-mhz-16-mhz-crystal-hc-49-s-low-profile.html

CBcracker

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #13 on: August 05, 2013, 09:02:23 pm »
however the adapters cost at least three times of the attiny ;-) at least when I compare the prices from my usual sources!
The discussed attinys are in the range of 1€ up to 2.5€ per single piece, the adaptors in the range from 5€ to 14€ :-(

80c for the tiny85-20SU and 35c for an SOIC adapter:
http://www.futurlec.com/Atmel/ATTINY85-20SUpr.shtml

For prototyping, I agree going the DIP route is better.
Afterwards, whether you're making 10 boards or a one-off project I like SOIC.
With the tiny 85 you can program the SOIC by holding it on a SOIC adapter with your finger or a small clamp (I think I saw this on hackaday).
Once it's programmed, stick it to the back of a 10c plastic CR2032 holder, and solder your connections directly to the tiny85 leads.  Obviously if you have a lot external parts this doesn't work so well and a DIP would be better if you're not doing a small run custom PCB (or etching your own).


digistump

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Re: How about a Digispark for the ATTiny84 series of chips?
« Reply #14 on: August 05, 2013, 11:25:42 pm »
First of all - I'm following and considering all the points here - just don't have time to respond to how each of them fits in against the Pro plans - especially since the pro isn't fully fleshed out yet.


A few specific responses


@cboden - we're looking at rotating the power pins - right now you can already use them most breadboards with power rails - but you loose the VIN pin and they aren't as universal as if we rotate them - if we do we will duplicate them for backward compatibility.


@gogol - thanks for the table - you're right about the 1634 while we could then run it at 8mhz or 12mhz and still be able to do v-usb (with external crystal) - that steers me more towards the 167 where we could run it at 16mhz (16.5mhz is only needed when using an internal oscillator) and therefore make it very compatible with existing Digispark/Arduino code written for 16mhz.


Regarding DIP vs SOIC - I hate to say it but this isn't too much of a consideration anymore - if we put too much weight on that then we will be stuck with the old tech - I'd be more inclined to sell dirt cheap adapters (even pre-soldered ones) then pick a chip just because it is available in DIP.


@CBCracker - to run at 12.8Mhz the chip will have to have an internal oscillator that is user calibrated to 1% (same for 16.5Mhz) - and many of the chips don't have that. To run at 12Mhz an external crystal must be used because greater accuracy is required.


Regarding the 35 cent price of the crystal - 33 cents + 2x1 cent capacitors - sure you can find cheaper crystals but that price is for a SMT (wayyy smaller than the Tayda ones, which are as wide as a Digispark on their own) and not grey market - we carefully select what markets our parts come from, and that has paid off (failure rate remains about 0.2%) - Crystals and Attiny chips always come from reputable, guaranteed suppliers - to combine grey market crystals and super timing sensitive V-USB with production prices would be a bigger headache then I'd ever want to have.




Thoughts on the Attiny167? I really like the idea of 16k which is why I'd prefer that to the 87