NAV radio project update

Well, I have spent some time gathering all of the parts needed for the radio and have looked into a way to display the right numbers on the displays. I felt a bit victorious when I was fooling around with the PoKeys software and was able to display something with the LED matrix test.

I went ahead and connected all 8 digits, I also decided to switch to Visual Basic since I had a clear example of how to interact with the PoKeys and Display Driver boards. Since the NAV radio has 10 digits in total (of which the first digit of each display always shows ’1′) and the PoKeys and Display Driver board only allow for 8 digit manipulation, I was thinking of re-using some of the segments of the 4 active digits (the decimal point or ‘dp’ of the 2 rightmost digits are never used). However, the segments ‘b’ and ‘c’ of the first digit (which compose the ’1′) have a common cathode. This means that using the ‘dp’ of the 2 rightmost digits is not going to work. I then decided to use the rightmost ‘dp’ segment to steer both the ‘b’ and ‘c’ segments of the first digit. This would allow for direct manipulation which is required (as opposed to hard-wiring the digit ’1′, because no power in the plane means nothing to display). This posed a new problem, because the voltage is to low to display both segments via the ‘dp’ segment.

I am now looking into a solution with opto-couplers, a direct connection to GND and 2 lines from the +5V with appropriate resistors.

To be continued…