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.
The large brick-type open source PLC has 22 digital inputs, 6 analog inputs and 16 transistor outputs. It also features a SD card socket, 2 RS-232 ports, 1 RS-485 port, 1 USB device port and a JTAG port for programming and debugging.
Large Open Source PLC
All the source files including circuit diagrams for building the large open source PLC are available for download at the above link.
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 ATtiny2313 course is presented as a multi-part tutorial and covers software development and hardware development using the ATtiny2313 AVR microcontroller from Atmel.
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.