DIGILENT PmodRS232 Serial Converter and Interface Standard Module User Manual
- June 5, 2024
- DIGILENT
Table of Contents
PmodRS232™ Reference Manual
Revised May 24, 2016
This manual applies to the PmodRS232 rev. B
Overview
The Digilent PmodRS232 converts between digital logic voltage levels to RS232 voltage levels. The RS232 module is configured as a data communications equipment (DCE) device. It connects to data terminal equipment (DTE) devices, such as the serial port on a PC, using a straight-through cable.
Features include:
- Standard RS232 DB9 connector
- Optional RTS and CTS handshaking functions
- Small PCB size for flexible designs 1.0“ ×1.3” (2.5 cm × 3.3 cm)
- 6-pin Pmod connector with UART interface
- Example code available in the resource center
Functional Description
The PmodRS232 utilizes the Maxim Integrated MAX3232 transceiver to allow the system board to communicate with UART compatible devices or other components that use a serial interface.
Interfacing with the Pmod
The PmodRS232 communicates with the host board via the UART protocol. The arrangement of the pins is the old UART communication style so a crossover cable will be required if attaching this Pmod to one of the dedicated UART Pmod headers on a Digilent system board.
A pinout description table and diagram for the PmodRS232 are provided below:
| Pin | Signal | Description |
|---|---|---|
| 1 | CTS | Clear to Send |
| 2 | RTS | Ready to Send |
| 3 | TXD | Transmit Data |
| 4 | RXD | Receive Data |
| 5 | GND | Power Supply Ground |
| 6 | VCC | Power Supply (3.3V/5V) |
Table 1. Connector J1 pin descriptions.
| JP1 | JP2 | Communication |
|---|---|---|
| Unloaded | Pins 1 and 2 are shorted together | 3-wire communication |
Pin 1 connected to pin 1 of JP2 and
pin 2 connected to pin 2 of JP2| Pin 1 connected to pin 1 of JP1 and
pin 2 connected to pin 2 of JP2| 5-wire communication
Table 2. Jumper block settings.
There are two jumper blocks on the PmodRS232; JP1 and JP2. These jumper blocks
allow the PmodRS232 to communicate in either a 3-wire or 5-wire operation.
When the jumper block on JP2 is loaded and the block on JP1 is unloaded, the
onboard chip has its RTS and CTS lines tied together, indicating to the
MAX3232 that it is free to transfer data whenever it receives any and enable
3-wire communication. JP1 must be unloaded in this configuration to ensure
that pins 1 and 2 on the Pmod header are not shorted together which could
potentially damage the system board.
5-wire communication requires that pin 1 of JP1 is connected to pin 1 of JP2,
and that pin 2 of both JP1 and JP2 are tied together as well, effectively
allowing for CTS/RTS handshaking between the Pmod header and the on-board
chip. Both the fifth wire in this configuration and the third wire in the
3-wire communication is the ground signal line.
Any external power applied to the PmodRS232 must be within 3V 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 mils apart. The PCB is 1 inch long on the sides parallel to the pins on the pin header and 1.3 inches long on the sides perpendicular to the pins on the pin header. The DB9 connector adds an additional 0.25 inches to the length of the PCB that is parallel to pins on the pin header.
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