USB to Serial Port Adapters, chips and adapters

There are several devices on the market to bridge the gap from a serial port (UART, SCI…) on your MCU to the USB bus. This page isn’t intended to discuss the end user USB products for adding a RS-232 port to your Macintosh, but much of the information below applies to them. Below is some information on some of the USB to RS-232 adapters I am aware of.

FTDI (Future Technology Devices International) produces several chips:
FT232H – Single Channel Hi-Speed USB to Multipurpose UART/FIFO IC
FT2232H – Hi-Speed USB 2.0 – Dual UART/FIFO Converter
FT4232H – Hi-Speed USB 2.0 – Quad UART Converter
FT232R – Single USB 2.0 to Serial UART Converter IC.
FT232B – Single USB to UART Converter ICs

Most support arbitrary baud rates, so non standard baud rates, like 3030 baud (used by Lionel) or 10417 baud (for the automotive LIN bus, see SAE specification J2602) are obtainable. FTDI has two different drivers available for their chips which can cause a problem on OS X systems. According to a FTDI FAE:
“With Mac OS X, our VCP and D2XX drivers are mutually exclusive.  You can only have one driver installed at a time. With Linux and Windows, you can have both drivers installed with no problems”.
So this is a major pain in the neck if you don’t understand what is going on.
If you need an adapter based on the FTDI chip that supplies +5 volts to the RS-232 connector from the USB bus, check out
Check out the FTDI D2XX class for XOJO (formerly RealBasic) here.

Prolific Produces two devices:
PL-2303HX-Edition(Rev D)
Their drivers do not support arbitrary baud rates. They seem to be limited to this list found in this code found on Prolific’s web site.
75, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14400, 19200, 28800, 38400, 57600, 115200, 230400, 460800, 614400, 921600, 1228800, 2457600, 3000000, 6000000
The newer Rev D device also supports 12,000,000 baud.

Texas Instruments offers this one with OS X drivers:
This device has been around for a long time. The SLLA170F document describes the drivers and TI’s support. The drivers can be downloaded from:

CYUSBS232, CYUSBS234, and CYUSBS236 with asynchronous serial, I2C, and SPI support.
OS X compatibility note:

Silicon Labs
The CP2110 data sheet is here:
Support is described here:
Driver download:

Other Hardware

Roving Networks
AAA Battery powered Wi-Fi serial Adapter. Supports many protocols.

WiSnap AAA
WiFi to RS-232 serial. Compatible with any WiFi device.

Lemos International
RS-422 with jumpers for echo, termination, and slew rate options. Based on the FTDI chip.

Author: admin on April 23, 2014

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