Hello, I have worked before with building schematics and PCBs with modules, now I am looking to shrink my projects even further by just using components and ICs. This is my first endeavor creating a simple Arduino-like microcontroller. I've been reading datasheets and looking at others' schematics. I believe I've created a basic microcontroller with the atmeaga328p and ft232rl that can switch between battery and USB power. I just would like some confirmation that it does work or corrections that I need to make.
I would also appreciate it if anyone had any good resources into learning more about these components and how to properly use them so I don't have to get confirmation from someone else that my schematics work properly.
I appreciate you taking the time to help.
microcontroller_schematic.pdf (56.3 KB)
Missing the required bypass caps 0.1uF from Vcc to ground and the optional Vref to ground.
Well, the project I am working on has only 2 cm worth of space on one axis, so the board I will use will have to be 100% custom. However, it probably would be a good idea to get one of these and learn how it works, or at least study the schematics for this board. Thanks for the suggestion!
Oh, good call. Thanks for noticing that!
Are you going to add a 16MHz crystal ?
Then why are you including an FT232RL ?
Yeah I still need the 16MHz crystal. Then the FT232RL is only about 1 cm long, so it will be able to fit when placed upright, the board is going to be somewhere around 2cm by 10cm.
You are aware that you need a programmer unless you're buying a chip with the Arduino bootloader preprogrammed right?
Do you need 16MHz? If you bootload 8MHz internal using the MiniCore core you can use the unused crystal pins as GPIO. They are referred to as pins 20 and 21. The MiniCore core is available through the IDE boards manager.
Yeah, I am going to hook it up to an arduino uno to upload the bootloader.
I have never heard of MiniCore before. I will have to do some research into it.
In that case you're missing a connector for the programming pins. Furthermore, the reset pin and the VCC pin of the microcontroller are connected to different power nets.
Edit:
You also should figure out what to connect the regulator tab pin to. It's most likely a part of the thermal design and should be connected appropriately.
I recommend study other minimalist boards, so you can see what at a minimum you need to include. You won't miss things like bypass caps, pull-up resistors, etc. The Pro Mini is excellent to study. Or even better the ProtoSnap Pro Mini, which includes the FTDI. It is retired, but still good to study the schematic and get inspiration, and there are clones available through eBay and other online shops. https://www.sparkfun.com/tutorials/303
I also highly recommend study the DFRobot Beetle. https://www.dfrobot.com/product-1075.html
It is a beautiful minimalist design and may be ideal considering you are interested in a USB interface.