As such, when the controller transfers logic for turning the segments to on/off, this is passed to all of the seven-segments at the same time. With the multiplexing technique, multiple seven-segments are interfaced with a controller and the respective data lines of all the segments are shorted. This way the seven-segment is always active and ready to turn its LEDs on/off according to the logical signal at its data pins (a, b, c, d, e, f, g, and dp). Similarly, when a single common-anode, seven-segment is interfaced with a controller, the common-anode terminal is typically hard-wired to VCC. When a single common-cathode, seven-segment is interfaced with a controller, the common-cathode terminal is usually hard-wired to ground. There are two types of seven-segment displays: common-cathode and common-anode. Otherwise, direct multiplexing would require at least 16 digital I/O pins. This way only three pins of the controller are engaged to control eight of the seven-segment displays. It uses an SPI interface to communicate with the controller. MAX7219 is one such LED driver IC that allows multiplexing of up to eight of the seven-segment displays. There are also several seven-segment display driver ICs that can perform the multiplexing technique and use standard serial interfaces to communicate with a controller. However, many seven-segment displays can be interfaced with a controller using the multiplexing technique.īy using this technique, the number of pins required to interface multiple seven-segments with a controller can be greatly reduced. Generally, the number of digital I/O pins on any controller are limited. If each seven-segment is interfaced independently with the controller (such as Arduino), several digital I/O channels are needed. If more digits are required, then more segments are necessary. The seven-segment unit can only display a single digit. In the previous tutorial, we discovered that interfacing a single, seven-segment display requires eight or nine connections. This option is typically more cost-effective than full LCD displays. These display units are ideal for displaying numbers or letters.įor example, they’re often used as a display unit in cost-sensitive applications where an embedded system may only require numeric information, such as a digital clock or a token display board. A seven-segment display is comprised of a unit of eight LEDs and seven of which are bar-shape and one is a dot. In the previous tutorial, we learned how to interface a seven-segment display with Arduino.
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