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NexGen Flight Simulator: Hacking the Navigation Computer Display June 6, 2013

Posted by phoenixcomm in 16 Segment driver, Aircraft, Arduino, CP-1252/ASN-128, DIY Aircraft Cockpit, Embedded CPU's, Ethernet, Flight Simulation, Hardware, Indicator Lamps, Multi Function Display, ps2 keybaord, Semiconductors.
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CP-1252This is the CP-1252/ASN-128 Navigation Computer Display.  The NCD was originally designed for Doppler  navigation, but will work in my application. I have reprinted the Analysis of this from my WordPress Blog (22Apr2011)

The Analysis:  The NCD is comprised of 4 groups: Display, Keyboard, Rotary Switches, and Thumb Wheel Switches.  The Display is comprised of 4 16-segment and 13 7-segment PinLite lamps, and two LED’s.  The keyboard is comprised of a 10 key number pad and 4 special keys, it also encodes A-Z. There are two rotary switches, and two thumbwheel switches as well. I also found a users guide, TM-1-1520-238-10 pages 3-34 through 3-46 on the web.

In it’s dim past it had been converted to a flight sim, and the only thing left whrere: the display, switches, light plate, and lots of wire. Each component, had each of their connection(s) brought out in to a header.

The Plan: As it is almost impossible to find a 16-segment display driver, but I really found two parts MAX6954 (SPI and QSPI interface), and MAX6955 (I2C interface). Both devices have the same programing model and have a I/O expander which could handle the keyboard. I have chosen to use the I2C interface. I have broken down the NCD into the following sub-units:

  • Two MAX6955AAX+ :
    • one will handle the 4 16-segment displays.
    • one will handle the 13 7-segment displays.
  • The keyboard will be interfaced via a standard Ps2 keyboard encoder that will be harvested from an old ps2 keyboard.
  • I will also need 2 bytes of I/O as well:
    • 1 byte of output to handle the two rotary switches, via two priority encoders (74LS148).
    • 1 byte for both thumbwheel switches (they are encoded to 4 bit BCD).
  • And lastly I need a USB interface to talk back to the IOP (IO Processor)

I also need a embedded microprocessor, the NCD information does not need to be super fast, as in reality it is only a dumb terminal, so an Arduino should be able to keep up with everything, if there are speed issues I will most likely switch to a TI Stellaris Launchpad module.   The NCD is either taking keystrokes from the pilot, or updating the display. In the words of the Outer Limits “There is nothing wrong with your television. Do not attempt to adjust the picture. We are now in control of the transmission. We control the horizontal and the vertical”. In the scheme of things this unit will only be another end point on the IOP which is sending the key strokes or and knob turns to the simulation processor. And in turn the NCD in effect listens to the NavGroup via the IOP for present positiontime to go etc.

 Keep Tuned in More to Come!

NexGen Flight Simulator Blog Index

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Arduino Trials and Tribulations, Part 1 April 30, 2011

Posted by phoenixcomm in 16 Segment driver, Arduino, DIY Aircraft Cockpit, Flight Simulation, Linux, ps2 keybaord, Software.
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Well I finally got my Arduino Duemilanove and prototype shields, there should be a Ethernet shield, and a LCD shield on its way. I wanted to try and use it on my Navigation Computer Display. To my horror I noticed that you could not stack on top of the prototype shield!

This really stinks I picked them up on ebay. I am going to have to modify the shields, grrr. I found the stacking headers at Adafruit for $1.50 per set.  Not bad.

The Analysis    I need to light four 16 segment lamps and thirteen 7 segment lamps, plus two lamps which will be bi-color leds. So thats lots of wire. My choice  of 16 segment display decoders are far and few between. The first one I looked at was an intersil ICM7243 interfaces with most microprocessors right on its memory bus. but can only handle 8 characters. So I would need two of them plus more glue to handle the last 7 segment display and the two lamps.  The next victims are the Maxim Max6954 with 4 wire interface, or the Max6955 with I2C interface. Other wise they both share the same specifications: They will drive up to 16 displays with mix of 7, 14, or 16 segments. It also has five GPIO pins that can be configured as a keyboard with up to 32 keys with n-key rollover, and built in debounce. The only down side is that they have eighteen  registers to configure the part.  I also need to interface the 2 rotary switches, and well as both thumb wheel switches.  I want to use a ps2 keyboard for testing the display system.

The Plan: Testing    I just go in two of the Max6955AAX+ in 36 pin SSOP package, and my eyes are to old, so I found Proto Advantage not only do they have a great price for the adapters plus they will mount the parts for me. In the meantime I happen to have a Max6954 in a 40 pin PDIP package. I will put it on a breadboard and wire it with a few displays and try to figure out the driver that I will need. – later

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