The goal of this project was to create a UART/serial black box that can be added to any project easily on the DE0-Nano. The only extra required hardware is a serial interface. I am using a CP2102 USB to UART bridge (http://www.silabs.com/Support%20Documents/TechnicalDocs/CP2102-9.pdf), but anything should work.

The project contains a sample application called loopback_test, which just sends all data it receives.

To use this in your own project, you will require the files uart.v, uart_fifo_dual_port_ram.qip, and uart_fifo.v. To make your life easier, also include uart_system.v and use uart_system as if it were the black box serial system. All parameters can be specified on uart_system.v. See the top of uart_system.v for details on what each parameter means.

The loopback_test block diagram is here:

I found the most convenient clock speed to work with to be 144MHz, which is easily produceable from a PLL. The UART divider can then produce most standard UART speeds. I succesfully tested up to 576kHz, but higher speeds should be possible.

Other features include:

• 1 / 2 stop bits
• None / Even / Odd parity
• 5- / 6- / 7- / 8-Bit Data
• TX/RX activity signals
• RX and TX FIFOs (default to 1kB each)