ATmega32u4 usb powered minimal bootloader and test circuit

Using Arduino Microcontrollers
1

Hello!

I'm new in electronics and I want to use a ATmega32u4 in a very compact project.
It will have no raw alimentation, only +5v from usb
I've done a lot of research and i built this two schematics:
one is the bootloader burning circuit
and the other is the minimal circuit to use the ATmega32u4 once the bootloader is burned

I'm actually not sure about my work and I really don't want to kill a ATmega32u4
(quite difficult to obtain where I live :cry: )

Could you help me to check my two schematics?

(Schematics in attachment)(sorry for bad english)

USBalimentationCircuit.png
USBalimentationCircuit.png710×647 69.3 KB

bootloaderBurnCircuit.png
bootloaderBurnCircuit.png1103×619 82.6 KB

2

Can't see any decoupling caps near the MCU. Use one 100nF on each of the chip's Vcc pins. Has to be physically connected near the chip.

By the way, why this particular chip? Are you comfortable to solder tqfp-44 SMD chip ?

3

actually I found this shematics (attachment)
the circuit in the attached pdf is rather simple and it is a commercial product so it surely correct.
i have ssome doubt about the necessity of having the two pgb at the usb and the 1M resistor at the crystal.
however you are right i need caps.

I'd like to use the atmega32u4 because it has usb and it is quite simple to programm...
the package is the TQFP standard, not a problem for heatgun soldering

P.S. using the beetle shematics i've done my version of it (removing pgb1010 and mabybe crstal resistor)

Beetle Sch.pdf (80.4 KB)

beetleSchematics.png
beetleSchematics.png756×603 74.1 KB

4

Yes you can do away with the usb protection devices and the 1 M resistor. I would also incluse an ICSP header for burning bootloader

5

actually adding a ISP header for bootloader burning is a very good idea.
it would simplify the building process
how can I do it?
sorry probably it is quite a stupid question

6

Google icsp to find out the pinout or check out the schematic of any arduino. Thay all have an icsp header.

7

thank you!