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STM32F103 min system with USB-TTL converter?

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bjdhjy888:
Hi,

     I recently managed to build my own STM32F103 min. system on a PCB. I was so happy about it. I flashed my LED blinking .hex file onto it, using someone else's USB-TTL module.

     I wanted to learn more, so I designed and improved my STM32F103 system with my own USB-TTL circuit added onboard. But no .hex file could be flashed onto it. (I used FlyMCU for the flashing).

     I then used my multimeter to check the voltages of my AMS1117-3.3 chip and noticed its output voltages were too high at 4.5V.

     I used FT232RL SSOP-28 for the conversion.

     I also reviewed my schematic and PCB layout and did find an error that one of the pins of my AMS1117-3.3 was not linked to GND of my micro USB.

     However, even after I fixed it using a flying lead on my PCB, the problem remained, i.e., I could not communicate with my STM32.

     Could someone on here help me review my schematic? Thank you so much!

ataradov:
Someone probably can. Why not attach the schematic here?

bjdhjy888:
Thank you.
Here is my schematic. I apologize if they don't look too professional, as I'm a newbie.
Would someone please help me find out where I did wrong? (The system worked perfectly before I adeed my FT232RL and AMS1117.)

Psi:
Ok, one thing i will say.
Ya should wire the ft232rl 3.3v output pin to vccio instead of using 5V from USB.
Then TX/RX are 3.3V level and will match the STM32

I can't recall which pins on STM32 are 5V tolerant.
But if the pin you're using for TX is not 5V tolerant it will backfeed 5V onto the STM32 VCC and this will cause major problems

Also please correct all the SCH pin names to match the actual IC pins. I assume you just repurposed some other sch component?

There's lots of stuff in that SCH that i have no idea what it's doing.

bjdhjy888:
Yes, I am correcting my SCH. Thanks.
I hope my SCH will be easy for people to read once it's corrected. 

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