The Display Board consists of 3 displays with 7 segments with common anode and with 4 digits each, two 8 + 8-way connectors, a series of PNP transistors and resistors. The control of the displays takes place in multiplex mode, ie by connecting in parallel the equal segments of all the displays (all the A together, the B together etc.), simplifying the control and thus avoiding the use of a large number of lines (84 for the precision). The lines common to the segments of the 12 digit LEDs form a bus on which to send data from time to time intended for a digit; each display is switched on when the corresponding signals pass on the bus, thanks to a PNP transistor acting as a static switch, which closes the common anode to positive.

This board is part of the project "Frequency and Clock Generator" published in the our blog, working in conjunction with the Matrix LED board code FT1286M (not included, see related products), can still be used in other applications.