3 Digit Dot Matrix Display with SPI interface is an advanced version of recently published 7×5 Dot Matrix Character Generator project. This design is more complex as it contains 4 microcontrollers. Three PIC16F88 were used to control 7×5 Dot Matrix Displays, one for each segment. All Slave modules are identical except for their address. Additional PIC/Display units can be added if required, just assign to each Slave a unique address by changing DigitAddress variable in the source code. SPI Master was implemented with PIC16F876A MCU. Each segment can be individually controlled by sending its address and data bytes in ASCII code via 2 line serial communication interface. One line for clock and the other for data. In the next figure design prototype board is shown, click it for higher resolution picture. As you can see 3 Solderless Breadboards were used to build the circuit.
Currently only numbers 0-9 and a few selected letters are supported like A,B,C,I,P. For additional characters you’ll need to modify Slave source code to generate a correct display sequence. More information can be found in the assembly code available at the bottom of the page. Here is the design schematic. Master PIC operates with 20MHz clock source.
Click to download design assembly source code,2 files (Mater/Slave). You may also be interested in similar post about SPI communication like 7-Segment Display with SPI PIC16F876A.