- General Info
- Specifications
- Pinouts
- Images
- Troubleshooting
- Applications
DESCRIPTION
The USB-TTL-33 is a professional quality, USB powered, bi-directional USB to 3.3V TTL converter. It is a combination of two products USB to RS232 Adapter (USB-232-2) and RS232 to 3.3V TTL Converter (TTL-232-33P). It can convert any standard full duplex USB port to 3.3V TTL and vice versa. The unit is powered from the USB port so no external power is necessary. It also supports data direction auto-turnaround requiring no flow control. The USB-TTL-33 has a USB type A female connector on the USB side and either a DB9 male connector or 5-way terminal block on the TTL side. The separate terminal block is included in the package. This converter operates from 300 to 115,200 Baud.
The USB-TTL-33 uses the latest FTDI chipset and is fully compatible with (32 /64 bits) versions of Windows 11, 10, 8.1, 8, 7, Vista, XP, and 98: Windows Server 2022, 2019, 2016, 2012 R2, 2012, 2008 R2, 2008, 2003 R2, 2003 Mac 10.3 â€" 10.15, and Linux.
TTL VOLTAGE LEVELS
TTL INPUT | TTL OUTPUT |
HIGH (>2.0) | HIGH (3.3V) |
LOW (<0.8)< /td> | LOW (0.0V) |
FEATURES
- Plug-and-Play (Hot-pluggable)
- USB 1.1 and 2.0 Compatible
- Port Powered - No External Power Needed
- Supports 300 Baud to 115,200 baud
- 3 Feet (1m) Cable for Convenience
- Transmit/Receive LED Indicators
- Data Direction Auto-turnaround - No Flow Control Necessary
- Internal 128/385 Byte TX/RX Buffers
- No IRQs, IO, DMA Required. No IRQ Conflicts
- Supports Remote Wakeup and Power Management
- Easy to Install Included Drivers
- Built-in 600W Surge and 15KV Static Protection
- 5 Year Manufacturer's Warranty
- RoHS 3, CE, FCC and REACH Certified

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ISO 9001:2015 QUALITY MANAGEMENT

Our internationally recognized ISO 9001:2015 Quality Management System (Cert. No. 743003912) with a scope of Design, Sales, Distribution of Data Communication and IT Support Services was recognized and certified by TÜV Rheinland of North America known for its very demanding and stringent requirements. For more details see our Quality Policy.
COMMUNICATION | |
STANDARDS: | USB 2.0 and 1.1 Standards - EIA/TIA RS-232C Standard |
OPERATING SYSTEM: | Windows 8.1 (32/64), Windows 8 (32/64), Windows 7 (32/64), Vista (32/64), Server 2012, Server 2008 R2, Server 2008, Server 2003, XP (32/64), 2000, 98Se, CE, Mac 8/9/X, Linux and Android |
BAUD RATES: | From 300 Baud To 115,200 baud |
CONNECTOR TYPES: | USB Side: Type A Female and TTL Side: DB9 Male or 5 Position Terminal Block |
DISTANCE: | USB Side: 10 ft (3m) and TTL Side: 10 ft (3m) |
LED INDICATIONS: | RS232: TX and RX |
DRIVERS: | FTDI drivers are included in package |
ELECTRICAL | |
POWER SOURCE: | Port Powered From USB Port |
CURRENT CONSUMPTION: | Less Than 100 mA |
STATIC PROTECTION: | 15KV Electric Static Discharge (ESD) Protection |
SURGE PROTECTION: | 600W Surge Protection |
MECHANICAL | |
WEIGHT: | 3.2oz (107.8 grams) |
DIMENSIONS: |
RS-232/TTL
Housing: 5.49 X 1.42 X 0.73
in (139.6 X 36.1 X 18.6 mm) Cable Length: 3 ft (1m) |
ENVIRONMENTAL | |
OPERATING TEMP.: | 14ºF to 140ºF (-10ºC to 60ºC) |
STORAGE TEMP.: | -40ºF to 185ºF (-40ºC to 85ºC) |
OPERATING HUMIDITY: | 5% To 95% - No Condensation |
QUALITY | |
PRODUCT SAFETY: | CE, FCC and RoHS Conformance Certified |
QUALITY MANAGEMENT: | Manufactured and Distributed to ISO 9001:2015 QMS |
MEAN TIME BEFORE FAILURE: | 427,056 Hours |
RELIABILITY: | Low Failure Rate - 99+% Reliability Since Inception |
WARRANTY: | 5 Year Replacement Warranty |
RS232 Side DB9 Female
Signal | DCD | DTR | DSR | RTS | CTS | TX | RX | GND |
Pin # | 1 | 4 | 6 | 7 | 8 | 2 | 3 | 5 |
Function | TIED | TIED | TX | RX | GND |

3.3V TTL Side DB9 Male or Terminal Block
Signal | NC | TTL IN | TTL OUT | NC | GND |
Pin # | 1 | 2 | 3 | 4 | 5 |
Function | NC | TTL IN | TTL OUT | NC | GND |










Using one USB-TTL-33 unit:
- Check that all connections comply with the connection diagrams.
- Perform a loop back test on one unit:
-
- Connect the IN to OUT on the TTL port.
- Connect the USB connector to the PC USB port.
- Running a hyper terminal program on the PC, send ASCII characters to the USB-TTL-33 converter from one PC port, and check that the characters are received at the same PC port. This tests that the transmit and receive functions of the USB-TTL-33 unit is working properly.
Using two USB-TTL-33 units:
- Check that all connections comply with the connection diagrams.
- Perform a loop back test on two units:
-
- Connect the two TTL ports.
- Connect the two USB connectors to two PC USB ports.
- Running hyper terminal programs on both PCs, send ASCII characters to the USB-TTL-33 converter from one PC port, and check that the characters are received at the 2nd PC port. Repeat the test in the opposite direction. This tests that the transmit and receive functions of both USB-TTL-33 units are working properly.
Download FREE FULL VERSION AccessPort Advanced Serial Monitor, Simulation and Data Analysis Software Tool. This software tool is great for testing converters. Supports Windows 98/XP/VISTA/WIN 7/WIN 8/WIN 10. DOWNLOAD SOFTWARE AND USER MANUAL
Below are some of the USB to 3.3V TTL Converter applications.
