I bought Pro Micro board based on ATmega32u4. All software and driver seem to work properly. But..
First problem is when I upload a new sketch to the board, its program storage doesn't clean. And every new sketch takes more and more available memory. And another thing that follows it - I can't burn bootloader via IDE.
The second problem or maybe strange behavior of the board is that it increases delays after power down/ power up. For example, when I upload simple sketch, that makes LED blinking once a second - use delay(1000) in my code - straight after uploading it works properly. But after the board turn off/ turn on LED becomes blinking once in ~8-9 seconds.
Did anybody meet such problem before?
Or maybe any ideas?
Perhaps you bought it from the same seller memoric77 got his from. The symptom sounds similar. You need to contact the seller because they are selling these with defective bootloaders. I recommend burning the bootloader. Do you have another Arduino of some sort?
Thanks to dmjlambert the second problem was solved. I burned new bootloader using Arduino Nano board.
But the first strange thing is still here.
When I upload even empty sketch like this:
void setup() {
}
void loop() {
}
that I receive as result:
Sketch uses 3,916 bytes (13%) of program storage space. Maximum is 28,672 bytes.
Global variables use 148 bytes (5%) of dynamic memory, leaving 2,412 bytes for local variables. Maximum is 2,560 bytes.
You should notice that each time you upload that empty sketch, even if you do it over and over, the number of bytes the sketch uses for program and variables does not rise. It stays the same. Each time you compile and upload a sketch, the processor is erased and new program loaded. The only part of the processor that is not erased is the bootloader area in Flash memory.
dmjlambert:
You should notice that each time you upload that empty sketch, even if you do it over and over, the number of bytes the sketch uses for program and variables does not rise. It stays the same.
You're right. When I upload this empty sketch to Pro Micro, it takes every time the same storage space - 3,916 bytes.
But why the same empty sketch use only 450 bytes when I upload it to Nano or Uno?
I think it is not normal.
It is normal for ATmega32U4-based Arduinos. In ATmega328P-based Arduinos such as Uno or Nano the USB-to-serial functionality is offloaded to a separate chip. ATmega32U4 uses a built in USB port and the processing that happens in the background to make USB features work takes some room.