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2v support
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2v support

by DCInnovation on Wed Mar 23, 2022 12:44 pm

Hello,

I purchased a USBtinyISP to program a board where Vcc is 1.8v. After pounding my head against a wall for a while a stripped the parts off that couldn't go above 1.8v and left the microcontroller. I noticed that It wouldn't program below 2.6v and finally visited the HELP! section of the webpage and saw that it won't work below 2.5v.

Why is it advertised to program boards below 2.5v if it can't? or am I missing something?

Sincerely,
-Confused

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Re: 2v support

by Franklin97355 on Wed Mar 23, 2022 4:09 pm

What are you trying to program and where did you find the info about the voltage below which it would not program?

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Re: 2v support

by DCInnovation on Mon Mar 28, 2022 7:34 pm

In the help section. I am planning to simply add either a level shifter to the device or lower the 5v rail to 3.3v

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Re: 2v support

by DCInnovation on Mon Mar 28, 2022 7:36 pm

Not sure if it will run on 3.3v though because of the 12mhz clock speed

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Re: 2v support

by Franklin97355 on Mon Mar 28, 2022 8:38 pm

According to the documents
"Version 2.0 which is almost certainly what you've got, uses a level shifter so that if the jumper is not in place, it will use whatever the target voltage is, a lot better for your low-voltage devices!

So, if you have a device that needs to run at 3.3V, don't have the jumper in place!"

So you power the USBTinyISP with 5 volts but not the chip. Is that what you are doing?

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Re: 2v support

by adafruit2 on Mon Mar 28, 2022 9:28 pm

its been a very long time but we dont know we've programmed 2V boards with the usbtinyisp, where does it say it does?

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Re: 2v support

by DCInnovation on Mon Mar 28, 2022 10:29 pm

Looks like it can based on the datasheet! Hopefully this works and helps others

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Re: 2v support

by adafruit2 on Tue Mar 29, 2022 11:09 am

ok the chip's datasheet isnt the same as the product datasheet or specifications. e.g. if a tire is rated to 250mph that doesnt mean the car can go 250 mph.

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Re: 2v support

by DCInnovation on Tue Apr 05, 2022 4:32 pm

Okay hopefully this helps someone out there. I was able program a 1.8v target by cutting the trace that connects the system to 5v, and soldering wires to a 3.3v source. when the microcontroller is powered by 5v the minimum voltage on a pin is 2.5 to get a logic high. That is why the help section says to use a 2.5v minimum target ("capture2.png" attachment).
Capture2.png
Capture2.png (66.14 KiB) Viewed 611 times


Once I got the 3.3v power to the microcontroller it registers 1.8v as a logic high.

The product page makes it sound like 2v is supported out of the box. Perhaps this is due to batch variations.

Let me know if you need more info!

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Re: 2v support

by adafruit2 on Tue Apr 05, 2022 6:59 pm

where does it say 2V is supported? we'll update the text

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Please be positive and constructive with your questions and comments.