32x40 dot matrix graphic displays
Created: Sep 16, 2014
No description available.
Dot matrix graphic display is a common electronic project; it is vastly used on streets and commercial places for advertisements. It comes with various sizes depending on the application and operation of the project. Although it is far way inferior to HD (high definition) screen display, still it is another way of showing off compared to traditional posters.
This project uses an IC intended for dot matrix application to lessen the components compared to typical LED drivers. The PCF8578 is a row and column driver, and the PCF8579 is a column driver. These are designed to drive dot matrix graphic displays at multiplex rates of 1:8, 1:16, 1:24, or 1:32. The PCF8578 has 40 outputs, of which 24 are programmable and conﬁgurable for the following ratios of rows/columns: 32x8, 24x16, 16x24 or 8x32. For larger systems, PCF8579s are used in conjunction with the PCF8578 with up to thirty-two cascaded PCF8579s capable of driving up to 40,960 dots. The sub-address pins (A0 to A3) of the PCF8579 are connected to VSS or VDD to represent the desired hardware sub-address code in multiple device applications.
The timing signals are derived from the on-chip oscillator, whose frequency is determined by the value of the resistor connected between pin OSC and pin VSS. PCF8578 and PCF8579 are compatible with most microcontrollers and communicate via a two-line bidirectional bus (I2C-bus).