I'm experimenting with lots of digital components lately and I needed to be able to see what is on the output of the digital bus, so I decided to make this little hexadecimal display to help with that. Additionally this display will be helpful as an output for my CPU project I am working on.

How it works

The display uses just two 7447 4 bit 7 segment decoder ICs for its logic. These ICs are super helpful for my application and greatly simplify the construction of the module. The 8 bit value is taken in from the top of the module, where there are some pulldown resistors so that there is no floating inputs fed to the decoder ICs. The LSB part of the 8 bit value (the lower 4 bits) is fed to the top 7447, with the MSB fed to the bottom one. I've then connected the 7 segment displays so that the left digit is LSB and the right is MSB. these displays are both common anode so there is no inversion required to drive the display. Additionally the 7447 has open collector outputs so that the digits can be driven directly.

Construction

The whole module was put together on a bit of protoboard and fits quite nicely. These boards get a bit hectic when you have this many components on them but it I didn't have any issues when constructing it. The power for the module is supplied through a pin header separate from the 8 pin input. For the power rails I used resistor lead offcuts to make solid rows so that it was easy to connect power to the ICs and the displays.

Overall I'm happy with how it came out, its a little rough in some parts but its mostly a tool so it will suffice.