I see lot of chip from Atmel company like AT89C2051,AT89S52,Atmega32,P89V51RD2.

Suppose I write a code for ATMEGA32 which blink one LED after 10 milliseconds. Can I use the same code for AT89C2051, AT89S52, P89V51RD2 if I change the port?

So if I buy one USB ISP programmer for Atmega32 MCU can I use it to program AT89C2051, AT89S52 also? Or does anybody compare the chip in terms of compiler, programmer, coding language, development board etc.?

There are two power supply sources in the following diagram - USB and 12V. Only one power supply can be connected at the same time. I am trying to disable power to FT232 whenever 12V is plugged in. In that case FT232 should not be powered, but MCU will be powered. However, when USB is connected, both FT232 and MCU should be powered. I tried to use Schottky diodes(BAT54C) but I'm not sure if this is correct way.

Also - would USB power harm voltage regulator in the second case?

I am creating a circuit in which a MCU (STM32) must drive 12VDC outputs, and wanted to make sure there wasn't anything missing in my driver circuit for the outputs.

-R1 is the inrush current limiting resistor
-R2 is the pull-down resister to keep the mosfet gate low if the MCU pin floats,
-D1 is the flyback diode, for protection against inductive loads, which will be a use case.

PS: I forgot to change the diode in the circuit, the actual part number is GSD2004W

The load will be connected to the 12V power line and the ground will be switched via the out pin.

The expected load will be practically anything as long as it is 12V and less than 250mA. But there will definitely be relay coils, indicator lights, and solid state relays attached to the output.

If there is anything I am missing that would be necessary or even a good idea or small improvement to include? I just don't want to spin a board with this and find out something wasn't working as intended, so some assurance would be nice.