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ItsyBitsy board specifications
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ItsyBitsy board specifications

by kscharf on Tue Jun 21, 2022 8:20 am

Adafruit has published official specs for the Feather, so anyone that wants to make a compatible format feather board or wing has the details. However, I've searched for layout specs for the ItsyBitsy format, and haven't found any.
I was thinking of making a feather using the AVR128DB-28, but for my own uses the ItsyBitsy format might make more sense as I don't need the on board battery charger. Also, it appears that the Feather MUST use 3.3v I/O signals, while the ItsyBitsy can go with either 3.3v or 5v.
As a KiCad learning project, I may very well attempt to layout both a feather and an itsybitsy, but I'd like to see some official specs on the ItsyBitsy board format, if they exist.

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Re: ItsyBitsy board specifications

by dastels on Tue Jun 21, 2022 9:08 am

The logic level voltage entirely depends on the MCU. None of the current ItsyBitsy models use a 5v MCU.

What, exactly, do you mean by "official specs"?

Dave

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Re: ItsyBitsy board specifications

by adafruit_support_bill on Tue Jun 21, 2022 9:14 am

The Feather was designed from the ground-up to support an extensive ecosystem of compatible Wings and accessories from multiple sources - hence the published spec. The ItsyBitsy less ambitious in that respect. But we are starting to see some compatible stacking boards like the AirLift: https://www.adafruit.com/product/4363

I'll check with the designers to see if there is anything like a formal spec for the layout of the Itsy.

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Re: ItsyBitsy board specifications

by kscharf on Tue Jun 21, 2022 10:02 am

The 32U4 ItsyBitsy (https://www.adafruit.com/product/3677) DOES run at 5v.
By "official specs" I mean specs 'approved' by AdaFruit to maintain compatibility with all ItsyBitsy products.

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Re: ItsyBitsy board specifications

by adafruit2 on Wed Jun 22, 2022 12:21 pm

there isnt because it is not as firm a standard - it came before feather. if you post a pinout ill tell you if its 'compatible'

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Re: ItsyBitsy board specifications

by kscharf on Wed Jun 22, 2022 1:23 pm

Guess I'll follow the existing 32u4 pinout where it matches the avr128DB28 pins (does a 5v board need a 3v regulator on it?) putting the UPDI pin on the right hand row. Not sure where the PWM pins will land though (does that matter?).

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Re: ItsyBitsy board specifications

by adafruit2 on Wed Jun 22, 2022 1:27 pm

PWM pins arent force-specified. if its a 5V board, follow the itsy 32u4 5V. if its a 3V board can follow the M0 or M4 or 32u4 3V ones

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Re: ItsyBitsy board specifications

by kscharf on Thu Jun 23, 2022 8:10 am

Since the AVR128DB series will operate at either 5 or 3.3 volts AT THE SAME CLOCK SPEEDS (might not overclock as well at 3.3 volts though), I'm tempted to make the board a dual voltage design, maybe use an adjustable low drop out regulator with a solder jumper to select one of two voltage setting resistors (or just swap the resistor at build time).

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Re: ItsyBitsy board specifications

by adafruit2 on Sat Jun 25, 2022 12:54 am

sounds good!

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