Serial Converter Design with the FTDI FT232RL for Raspberry Pi, Zigbee, RS485, RS232 and TTL

Posted by Vytas Sinkevicius on

Many applications require converting one serial hardware protocol to another such as USB to Zigbee, Rspberry Pi Uart to RS485, RS232 tot TTL levels, or any mix of the above. The Serial Utility Tool (SUT) is designed around the FTDI FT232RL chip for converion from USB to the other formats.

SUT fully assembled:

 Schematic Page 1:



All of the circuitry for the converter can be powered from the USB port, in higher power applications, the design incorporates an optional power supply, the VP-PSDC-05-033. The heart of the design is the FTDI FT232RL USB converter IC. The TTL levels are available on the RJ11 jack or pin header.

Basic version with USB, Raspberry Pi and Zigbee headers.

Bottom side PCB view:

Schematic Page 2:



This schematic shows the Zigbee module connections, the Raspberry Pi Connections and the RS232 Interface. In some cases where only the USB to Zigbee are required (no other sections populated), there are jumpers available (R48 and R49) to provide a direct connection between the USB and Zigbee modules.

SUT and Raspberry Pi connected:


Schematic Page 3:


This schematic shows the RS485 connections. If the Raspberry Pi Uart is not used, or does not want to drive the RS485 direction, there is an Automatic Direction Circuit based on a 555 Timer. It senses whenever there are transmissions present on the TX line and switches the direction control of the RS485 drive IC, (the MAC3072 or equivalent). This circuit has been tested and used in applications running at 9600 BAUD all the way up to 115.2K BAUD with no problems - this is a staple in our tech department.

SUT in kit form:

Schematic Page 4:




I personally like lots of LED's, this circuit shows the logic for all the TX and RX LED's available for all the various in's and out's.

There you have it - a multi-use Serial Converter Tool!

Oh, almost forgot - the PCB design was done so the final assembly would fit into a standard SERPAC enclosure as shown:


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