The USB CDC driver for Atmel SAM ARM microcontrollers allows a USB microcontroller that is running the SAM-BA software to be configured as a virtual COM port on a PC.
This allows user software to be loaded to the microcontroller via a USB cable using the SAM-BA PC application software.
The article on Installing the SAM-BA USB CDC Driver for Atmel ARM Microcontroller in Windows shows how to install and test the driver.
Terminal emulator software is used to communicate with the embedded SAM-BA software on the microcontroller and request the SAM-BA software version number. This is done to test that the driver and connections are working properly.
This small brick-type PLC open source hardware project is based on an ARM7 microcontroller from Atmel. The PLC has 10 digital inputs, 8 digital outputs, 4 analog inputs, a real time clock, RS232 port, RS485 port, USB port and JTAG port.
More information and circuit diagrams are available at the above link.
Small Open Source PLC
This Simple ARM Board Open Source Hardware project uses the AT91SAM7S256 ARM7 microcontroller from Atmel. The page at the above link contains the source files for building and modifying the board (PCB and schematic), the Gerber output files and the circuit diagram in PDF format.
AT91SAM7S microcontrollers can be programmed via the USB port — no programming device is necessary. This tutorial explains how to program the AT91SAM7S256 microcontroller on a AT91SAM7S-EK evaluation board over the USB port using the SAM-BA in-system programming software from Atmel.
The tutorial includes information on where to download the SAM-BA software from and a video on how to load firmware to the AT91SAM7S microcontroller.