GPIO'4'Cars

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mctom
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Re: GPIO'4'Cars

Post by mctom »

zyssai wrote:
Thu Nov 24, 2022 8:43 pm
I'm just need to be sure that 3.3v to LM7833 will not burn it, but in the worst case I will burn one piece :lol:
For the moment I have no pull-up activated in the code, it seems to work like this, but the behavior will be different once soldered to the board.
You can skip power delivery from Arduino and just power your attiny as usual. No problems with 7833 then because it will work the way it's supposed to be used. :)

I think pull-ups may be activated by default, so you may have to disable them. I'm not sure about this, though.
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Re: GPIO'4'Cars

Post by zyssai »

mctom wrote:
Thu Nov 24, 2022 9:23 pm
You can skip power delivery from Arduino and just power your attiny as usual. No problems with 7833 then because it will work the way it's supposed to be used. :)
As simple as this, I missed it ;) it's perfect then.
mctom wrote:
Thu Nov 24, 2022 9:23 pm
I think pull-ups may be activated by default, so you may have to disable them. I'm not sure about this, though.
According to the code, it seems we need to write this to activate pull-up, but I have not tested it.

Code: Select all

pinMode(pin_input_12v, INPUT_PULLUP);

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Re: GPIO'4'Cars

Post by zyssai »

So after some "googling" session, it seems that the nano needs to be modified to be powered by 3.3v.

I looked at other Arduino models, and it appears that the Mini Pro 3.3v is the good choice, and can be used as an ISP programmer, as explained here.

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Re: GPIO'4'Cars

Post by mctom »

There are plenty of Arduino spin-offs and fakes, at least some of them should work at 3.3V.

Can Arduino interface generate a binary file to be written on target AVR, instead of writing it themselves?
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zyssai (Fri Nov 25, 2022 4:18 am)
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Re: GPIO'4'Cars

Post by joerg »

Can Arduino interface generate a binary file to be written on target AVR, instead of writing it themselves?
Yes, the path to it can be found in the log console.
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zyssai (Fri Nov 25, 2022 4:18 am)

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Re: GPIO'4'Cars

Post by zyssai »

In the worst case I will use classic programmer with avrdude ;)

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Re: GPIO'4'Cars

Post by jackinho »

Regarding the 3.3V vs. 5V problem: why not just use a logic level converter?
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zyssai (Sat Nov 26, 2022 5:02 pm)

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Re: GPIO'4'Cars

Post by mctom »

jackinho wrote:
Sat Nov 26, 2022 5:19 am
Regarding the 3.3V vs. 5V problem: why not just use a logic level converter?
Because the price is similar to an actual AVR programmer that handles 3.3V ;)

https://www.sparkfun.com/products/12009
https://www.ebay.fr/itm/173470207520
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Re: GPIO'4'Cars

Post by jackinho »

mctom wrote:
Sat Nov 26, 2022 7:10 pm
https://www.ebay.fr/itm/173470207520
Well, 60 days for delivery. Really?

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Re: GPIO'4'Cars

Post by mctom »

jackinho wrote:
Sat Nov 26, 2022 8:38 pm
Well, 60 days for delivery. Really?
That's not an issue at all, I offered a donation of a similar programmer to @zyssai if he wishes to try it. I have a few programming kits and I haven't used either of them in years. I would be very glad to pass it on to someone who will use it more.
I do believe that using the right tools yields better results in shorter time, than hacking the way to make one prototype work, and then have troubles making it repeatable in any way.

The voltage converter board, yes, I guess that would work. It's worth mentioning it has quite a limited speed, as it relies on pull-ups on the "output" side in either direction. To put that into perspective, SPI is faster than I2C exactly because SPI outputs have totem pole drivers.
In this application it would work, because the programming speed can be lowered. But it's worth remembering these simple level shifters are not an universal solution.
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Re: GPIO'4'Cars

Post by zyssai »

mctom wrote:
Sat Nov 26, 2022 9:06 pm
...
Thanks mctom. I think we will try the actual way, and see if it works ;)
I have ordered most of the parts, unfortunately I can't find any LM7833 anywhere. I don't know if it exist some replacement part.

Edit: ok I discovered the search tool of digikey, exactly what I need :twisted:
https://www.digikey.com/short/5bdnd3bc

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Re: GPIO'4'Cars

Post by mctom »

zyssai wrote:
Sat Nov 26, 2022 11:05 pm
I have ordered most of the parts, unfortunately I can't find any LM7833 anywhere. I don't know if it exist some replacement part.
There are plenty of similar chips, just look for anything with 7833 in their name, and the matching IC case. What case did you use?
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Re: GPIO'4'Cars

Post by zyssai »

mctom wrote:
Sat Nov 26, 2022 11:50 pm
There are plenty of similar chips, just look for anything with 7833 in their name, and the matching IC case. What case did you use?
I think I will keep TO-252, this way I do not need to modify PCB as it is in review by manufacturer.
The only consumption will be the Attiny so I think I can reduce current output.

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Re: GPIO'4'Cars

Post by mctom »

Yes you shouldn't worry about the current in this application, will probably be less than 10mA. :)
TO-252 is also known as DPAK, depends on the manufacturer. That can expand the choice if you include that in your search. :)
Also if you find a substitute, make sure the pin order is the same as in original LM7833 - it should be, but you never know.
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Re: GPIO'4'Cars

Post by zyssai »

mctom wrote:
Sun Nov 27, 2022 1:43 am
Yes you shouldn't worry about the current in this application, will probably be less than 10mA. :)
TO-252 is also known as DPAK, depends on the manufacturer. That can expand the choice if you include that in your search. :)
Also if you find a substitute, make sure the pin order is the same as in original LM7833 - it should be, but you never know.
Thanks :!:

So I came back to MCP1703, same package and pinout, seems to be around 200mA output current. Perfect ;)

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Re: GPIO'4'Cars

Post by joerg »

zyssai wrote:
Sun Nov 27, 2022 2:26 am
So I came back to MCP1703, same package and pinout, seems to be around 200mA output current. Perfect ;)
It's a good choice. I use this also on my interface board.
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