Minipro 3.3V uploading problem

hi,
I m getting trouble programming a minipro 3.3V 8MHz through an uno as an ISP: so far I managed to upload anything into minipro 3.3V without any problem using similar process and connexion so I just do not understand why it failed! I tried on 2 minipro 3.3V that now are fried (supposedly.... !)

It load the program but then it say at the end that there is a problem with serial that is not connected, and then it ends and then the minipro looks dead (no flashing light anymore, and device signature to 0x000000)

My process:
load arduino as ISP program in the UNO
connect the UNO and minipro
UNO -->minipro
3.3V -->VCC
GND-->GND
13-->13
12-->12
11-->11
10-->reset

select the blink program, select minipro and 3.3V&8MHz option, then ''upload using a programmer''.

Any idea of how to solve that? are they fried? I know it is a recurent problem, I have seen a lot of topics on uploading problems, but its difficult to found out what to do exactly
I m using arduino 1.8.13 and the arduino ISP look to be the 1.8

many thx for any advice and help,

Your UNO is 5V and mini pro is 3.3V. The mini pros are all damaged when you connected the 5V UNO pins to mini's 3.3V pins. You can buy an adafruit feather 328 that operates at 3.3V and try with a fresh mini pro 3.3V that you have not connected to an UNO.

Which component do you think would be damaged?

The only one I can think is the voltage regulator. I didn't find any information about whether applying 5 V to the output of the unpowered MIC5205 in the datasheet is harmful. I did find almost the same Q on EESE.

The 328 on the mini pro 3.3V. Since it is powered by 3.3V, it shouldn't be connected to the 5V UNO via the ICSP header.

Here is a table from the data sheet. No IO pins should receive voltage over VCC+0.5, so 3.3+0.5=3.8V would be the highest voltage the mini pro 3.3V can accept.
image

Ah, I see. I missed the "3.3V -->VCC". Thanks for the explanation.

That was mentioned at least 3.3 times in OP's post :smiley:
I don't want to appear senile or stereotyping or offensive but I find that younger people these days can't read and retain information beyond one line of message. It's pretty hard to communicate with them when they need your help and can't answer two questions in a single email you send them. Even some graduating senior college students exhibit this symptom. If I could figure out a way to get them to read, I might become the best educator of the 21st century.

I thought, @in0 thought that OP did program with connecting VCC(5V) to each other.
Since the 3.3V Pro mini works fine even at 5V (except the onboard regulator reverse voltageed).
So the word 3.3V does appear many times, but he actually overlooked only one line, 3.3V-> VCC

Thx guys for your answers, soon I got the new minipro, I will have a try with IO at 3.3V (I guess I can use a TTL level shifter?).
And will let you know.

Yes, you can even use two resistors to form a voltage divider. As long as your cable is short and your UNO's SPI data rate is low, you will be fine.