The data is sent using standard asynchronous RS-232C serial format: An explanation of serial RS-232 mouse pinout The TD pin is the pin that carries the data from the DTE to the DCE.Ī standard serial mouse takes 10 mA total current operating at a voltage range between 6 and 15 volts. Negative supply for the transmitter is taken from the TD pin. An optomechanical mouse (one that makes use of optical sensors) that has LEDs will require power to light those LEDs.ĭiodes are often used to take current from the DTR and RTS lines – intercepting the diodes and resistor. Serial device hardware implementationĪ serial mouse makes use of DTR (Data Terminal Ready) and RTS (Request to send) lines to generate approximately 5V of power for its microcontroller circuit. On average, a mouse will use about +5 volts to perform. Average mouse outputs range between +5V, -.5V and +12V. The data being sent must be at a level that can be understood by the receiver chip. The mouse then sends data to the computer’s receiver chip. The RS-232C port will have a number of output lines from which the mouse can take current (about 10mA). PC RS232 serial mouse voltage levels:Ī standard mouse expects a RS-232C output signal with an approximate 12V level as its input signal.

It is the mouse driver that is installed on the computer that receives the data packet and decodes it, then executing the appropriate action based on the instructions received. When this information changes, a data packet is transmitted by the mouse controller to the computer’s serial data interface controller.

The mouse controller takes note of the current mouse position as well as the state of the various sensors. Movement of the mouse as well as button clicks is detected by the sensors. With current technology, only a 9-pin connector is in use with most personal computers.Īn example of how RS232 serial port works with the help of the serial mouseĪ serial mouse comprises sensors, mouse controller, communication link, data interface, driver and software. With RS232, hot-plugging or hot-swapping is not supported, though it is sometimes possible to plug in a serial device and it will work while the computer is running. This is represented by voltage levels defined by the RS232 protocol. A common ground between the computer and the connected serial device is mandatory. RS232 allows for full-duplex communication – this means that both devices can interface with each other simultaneously. The data that is transferred between these two devices is transferred at a rate less than 20 kbps. This means that you can only connect two devices using a RS232 serial cable. Many motherboards also feature a COM port header which makes it possible to install a bracket with a DE-9 port.ĭespite the shortcomings and the technology advancements, RS-232 interfaces are still very much in use with large industrial machines, networking equipment and scientific instruments where point to point, low speed wired data connections is sufficient.Ī PC serial port interface is single ended. It is however possible to use an external USB-to-RS-232 converter or an internal expansion card with one or more serial ports to connect a RS-233 serial peripheral device to your computer. These shortcomings include low transmission speed, limited cable length, substantial voltage fluctuations, and limited multidrop capabilities. RS-232 has many shortcomings when compared to later technologies such as RS-422, RS-485 and even Ethernet. Universal Serial Bus (USB) has replaced the traditional RS-232 interface. Modern day computers seldom have RS-232 ports. It defines the electrical properties and the timing of signals, as well as the interpretation of signals, and the physical size and pinout configuration of a connector.

RS-232 is the common standard used in serial ports. The background of the 9 pin serial portįirst introduced in the 60s, RS-232 is a protocol that defines how the data is transferred, bit by bit from a Data Terminal Equipment (DTE) such as a computer terminal, to Data Communication Equipment (DCE) such as a modem. A RS-232 serial port was a standard feature of personal computers as it was the preferred way to connect modems, keyboards, mice, external storage and many other peripheral devices. The RS232C DE-9, often mistakenly referred to as a DB-9 port used to be the industry standard for serial data transmission.

Serial db9 connector