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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

Driving those pesky indicators. December 30, 2011

Posted by phoenixcomm in Arduino, Boeing 707, Boeing 727, DIY Aircraft Cockpit, F-18, Flight Simulation, Indicator Lamps, Power Systems, Relay.
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Well here we are again, and I am having to drive multiple of voltages for my indicator lamps…. This can be a pain in the rear… Let me see I have  5 volts, 12 volts, 28 volts. Take your pick..

You have several choices:

  1. Do nothing, just buy lots of power supplies.
  2. Change out all the lights to one voltage. (big bucks)
  3. Something else maybe?

Me I’m out there anyway so I’m going with you guessed it: ‘C’.

The Analysis: First a little background…
Rule #1:  Computers Logic (TTL) does not like voltages over 5 volts dc.
So how do you drive a 28 volt lamp from a computer?  There are several ways..

  1. Relays..(ADVANTECH PCLD-785B with 24 relays) This card retails for $240.00. Or you can find them used for about $50.00 on ebay. This tends to be some what costly as you have to buy the boards and then a driver for them. It’s more than little kludgy with tons of wire screwed down, on barrier strips. But it does work and its bullet prof. But remember all those power supplies.
  2. HEX INVERTER BUFFERS/DRIVERS WITH OPEN-COLLECTOR HIGH-VOLTAGE OUTPUTS SN5406 and SN7406 have minimum breakdown voltages of 30 Volts DC. But when they fail it could put raw 28 volts on your computer! Ouch!
  3. Optoisolator I like a little 6 pin dip a TIL111 will handle 0 to 30volts DC with TTL inputs.  If  you want you can buy them at Digi-Key for about 18 cents each, and if you look around you can buy them cheaper else where.   Add a few parts for decoding and latch, you can drive all of your lamps.

So lets see 18 cents x 64 optoisolators is less then $12.00. This means that with just 16 cards you could drive 1024 lamps…  But wait a minute I said DC right? (Who said we had to drive the lamps with AC). Now that we have DC you can easily create a divider or regulator for you lamps from one 28 volt power supply.

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