SparkFun
RS232 Breakout - ST3222 with DE9 Connector
· MPN: BOB-29197
This compact breakout makes it straightforward to connect 3.3V microcontroller projects to legacy RS232 serial equipment such as older computers, industrial ...
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This compact breakout makes it straightforward to connect 3.3V microcontroller projects to legacy RS232 serial equipment such as older computers, industrial machines, GPS modules and other devices using a DE9, also known as DB9, connector.
At the centre of the board is the ST3222 RS232 driver/transceiver from STMicroelectronics. It performs the voltage-level shifting between low-voltage TTL logic and the higher-voltage RS232 standard, converting 3.3V logic signals to RS232 levels and back again.
The female DE9 connector accepts an RS232 device cable directly, while the microcontroller side is broken out to a standard 0.1"-spaced, 9-pin plated through-hole header. The board also handles the TX/RX crossover internally, so you can connect TX to TX and RX to RX without needing to work out whether a null-modem or crossover cable is required.
Two mounting holes are included for securing the board into an enclosure or project. Documentation provided by the supplier includes the schematic, KiCad files, ST3222 datasheet and GitHub repository.
Features:
- DE9 Connector
- ST3222 RS-232 Driver/Transceiver
- 1x9 Plated Through-Hole (PTH) Header
- 2x Mounting Holes
- Handles the TX/RX signal crossover internally
- Low-power shutdown mode for battery-powered projects
Specifications:
- Microcontroller logic: 3.3V
- RS232 signal level: ±5V (or higher)
- Power supply voltage: 3.0V to 3.6V
- Data rate: up to 250Kbps
- Shutdown mode supply current: just 1mA
- Connector: female DE9 connector
- Header spacing: 0.1"-spaced
- Header: 9-pin plated through-hole (PTH) header
- Mounting holes: 2x
A useful interface board for projects that need reliable RS232 communication from modern 3.3V microcontrollers.
Jargon buster
Plain-language definitions for the technical terms used above.
- breakout
- A breakout board carries a small or fine-pitched component and brings its connections out to standard, breadboard- and header-friendly pins. Describing a part as a breakout means it can be wired into a project without soldering directly to the component's tiny contacts.
- GPS
- The US satellite navigation system used by GNSS receivers to calculate position and time. Support for GPS is important because it is widely available and often used together with other constellations for more reliable positioning.
- microcontroller
- A microcontroller is a small computer on a single chip that runs a stored program and controls connected inputs and outputs such as buttons, sensors, displays and communication interfaces. In a device built around one, it is the part that executes the code and coordinates the device's behaviour.
- PTH
- Plated through-hole means the pin holes are metal-lined so solder connects the pad on both sides of the board. It is useful for connectors and headers that need a strong mechanical and electrical connection.
- RS-232
- RS-232 is an older serial communication standard that uses higher, inverted signal voltages (typically around plus or minus 3 to 15 volts) rather than the low logic levels of modern microcontroller pins. When connecting RS-232 equipment to a microcontroller, you usually need an RS-232 transceiver or level converter rather than wiring it directly, or you risk damaging the pins.
- RX
- RX means receive, usually showing data being received by the board. An RX indicator LED can help with troubleshooting USB or serial communication.
- through-hole
- A mounting style where the component leads pass through holes in a circuit board and are soldered on the other side. Through-hole parts are often easier to handle and solder by hand, which is useful for classroom and hobby projects.
- TX
- TX means transmit, usually showing data being sent from the board. A TX indicator LED can help you see when the board is communicating or uploading code.
Find this product in
Prototyping & Wiring
RS232 Breakout Schematic
Schematic · 123.9 KB · Click any page to view full size
ST3222 Datasheet
Datasheet · 348.6 KB · Click any page to view full size
Supplier page — sparkfun.com
Supplier Description · 725.3 KB · Click any page to view full size
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