With altitude, airspeed and heading indicators as well as an RTH arrow and a better attitude indicator, it is starting to look like a proper HUD. I have made the indicators white-green to reduce the effects of limited chroma bandwidth, and the Armed warning is now black on yellow for the same reason.
The attitude indicator needs a boresight, and text rendering needs some tidying up – you can see the imperfections if you look closely. Next item to implement will be a battery meter. It will use colour to show battery status, progressing from green to yellow, orange and red as the voltage drops. I will also try to implement a generic “indicator” which can be used to display any kind of parameter. It will have a text label and an optional colour swatch or icon, which can change in response to the parameter. It can be used to show things such as GPS satellite count, temperature, current and so on.
Some time in the future I would also like to have analog gauges as an alternative to HUD-style tapes. You will be able to have the traditional “6-pack” instruments if you want to.
After some discussion with airbanana at RC Groups I am going to make another attempt to generate the overlay by genlocking and pixel switching, instead of using digital decoder and encoder ASICs. If this works it should use less current (at the moment my dev board and MCU draw about 0.5A). There 2 are ways I could do this. One is the method I tried earlier, using an AD724 clocked in sync with the colour subcarrier. Another possibility is the approach used here. Rossum is generating the entire composite signal including the colourburst using the SPI port. To do that he needed to overclock the MCU to a multiple of the colourburst frequency. But the SPI port can be driven by an external clock. I can obtain a clock signal in sync with the colourburst using an MC44144 and a comparator as I did previously, and try using that to drive the SPI. It will be some time before I can try either approach as I will need to fabricate a new board. In the meantime I will continue working on the graphics.