Pmod USBUART Reference Manual

The Digilent Pmod USBUART (Revision A) is a USB to UART Serial converter module capable of transfer rates upwards of 3 Mbaud.

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  • USB to serial UART interface
  • Micro USB connector
  • Option to power the system board through the FTDI chip
  • 6-pin Pmod connector with UART interface

Functional Description

The Pmod USBUART provides a USB to UART cross-conversion through the FTDI FT232RQ. Users may send data in either direction on the Pmod and receive the converted data in the appropriate format.

Interfacing with the Pmod

The Pmod USBUART communicates with the host board via the UART protocol. Users may either provide data through the USB port and have the on-board FTDI chip automatically translate the USB styled data into the UART protocol. Similarly, data provided through UART is automatically translated by the FTDI chip to the USB interface. Different speeds, parity, and other settings can be configured through a terminal emulator on your computer. The host is presumed to be an external component so RXD (pin 2) expects to have the Pmod receive data from an external host and TXD (pin 3) expects to transmit data from the Pmod to the host. Active low handshaking signals ~RTS (Request to send output) and ~CTS (clear to send input) are provided on pins 1 and 4, respectively.

Pinout Description Table

Header J1 Jumper JP1
Pin Signal Description Pin Signal Description
1 ~RTS Request to Send Output (active low) 1 LCL3V3 The attached system board is powered independently from the Pmod USBUART
2 RXD Receive data from host to Pmod 1 SYS3V3 The attached system board is powered through the on-board FTDI chip.
The FTDI chip can supply up to 50mA.
3 TXD Transmit data from Pmod to host
4 ~CTS Clear to Send Input (active low)
5 GND Power Supply Ground
6 VCC Power Supply

Any external power applied to the Pmod must be within 2.5V and 5.5V; however, it is recommended that Pmod is operated at 3.3V.

Physical Dimensions

The pins on the pin header are spaced 100 mil apart. The PCB is 1.0 inches long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.

Additional Information

The schematics of the Pmod USBUART are available here. Additional information about the FTDI FT232RQ including communication modes and specific timings of the chip can be found by checking out its datasheet here.

Example code demonstrating how to use the Pmod USBUART can be found on it's Resource Center here.

If you have any questions or comments about the Pmod USBUART, feel free to post them under the appropriate section (“Add-on Boards”) of the Digilent Forum.