Howto:C172P Cockpit Project

This Howto will develop into a detailed project plan for building a C172P Instrument Panel. While not a step by step guide, it will include details on the prototyping, design and building of a panel. The project includes the following major activities:

Open Identified Tasks

Task Description	Blocking Factors/Action Items/Progress	Status
Bench Power Supply	Finalize Design Purchase Aluminum Order 24 Pin Socket Figure out how to make square holes in aluminum without a laser. Make a Bending Brake Bend Some Tin (ok aluminum, but the traditional phrase says "tin".) Test what load Resistor on which voltage will turn on the power supply I suspect that 5 volts, 5 ohms, 1 amp will turn on the supply. That's 5 watts. Have 50 watt resistor. Drill Mounting Holes for Load Resistor Cut holes for Meters and Binding Posts (Banana Jacks) Mount the ATX power supply in the hand built case	Scheduled for Late October 2016
Flightgear Rasberry Pi Client	Using Node.js and possibly Rx.js Demonstrated Node server sending and receiving data to Flightgear properties telnet server Created Single Data Structure for all Flightgear properties Working with a list of these structures Investigate Exporting/Importing the data from XML files	Ongoing
Program an AtMega chip with SPI and I2C interfaces	Install AtMega Programming tools Initial demo without crystal Send and receive data from Raspberry Pi	Unstarted - Scheduled for Late October 2016
Port Expander Demo	3 to 8 or 4 to 8 demultiplexer SPI port Expander driven from Raspberry Pi Serial to Parallel from AtMega Light some LEDs Detect some switch transitions, on-off (Taxi Lights) on-off-on (KMA20 switches) momentary contact (frequency swap) Deal with debouncing	Unstarted - Scheduled for Q4 2016
Rotary Encoder Demo		Unstarted
Air Coil Demo		Unstarted
Frequency Display Demo		Unstarted
Template	Task List	Status
Template	Task List	Status

Description

The work product will match an actual C172P cockpit instrument panel as closely as possible given constraints of tool availability, time and money.

Versions:

1. A set of rotary encoders and switches in an overlay for a regular monitor
2. Expand the project to include items in the radio stack
3. Replace the monitor with individual instruments

Design Alternatives

• Instruments
  • Monitor Overlay
  • Individual Instruments
• Multi-value inputs
  • using potentiometers and ADC ports
  • Using magnetic encoders with:
    • AtMega driven pins
    • SPI
    • I2C
• Display of Numeric and Alphabetic data
  • driven by Maxim Max7221 on an SPI interface
  • driven directly by an AtMega processor
• Banks of switches and rotary encoders with a multiplexed parallel interface
• Raspberry Pi connected to one or more AtMega Processors via SPI or I2C
• Raspberry Pi connected to a 4 to 16 bit multiplexer to select SPI data
• Raspberry Pi responsible for interfacing raw data to flightgear property values
• Display of numeric and alphabetic data using 7 and 16 segment displays
  • drive with AtMega chip and Transistors
  • drive with Maxim Max7221CNG Integrated Circuit
• AtMega Processors with port expanders responsible for raw data
• AtMega Processors communicate with Raspberry Pi
  • Using SPI
  • Using I2C
• Telnet interface to Flightgear runs on Raspberry Pi
  • C programming language

== Code Development Activities

Client to Flightgear protocol

=== Client to AtMega protocol

Magnetic Encoders

• For Heading Adjusters on Instruments
• Replacement for Rotary Encoders
• Replacement for Potentiometers

Proof of Concept and Prototyping Activities

Client on PI

Communication with Flightgear using Telnet

• Change the value of a cockpit switch
• Read the value of a Com or Nav Radio's frequency
• Change a standby frequency
• Make a standby frequency the in use frequency
• Dim and brighten the instruments
• Move the throttle
• Move one of the control surfaces

SPI

• different speeds
• Error Detection and re-transmission
• Server to ATMega
• Server to Max7221
• Server to Port Expande.

Server to MCP23S17 16 bit port expander is working. Server can configure two MCP23S17 expanders one as 16 inputs, the other as 16 outputs. The outputs are used to select banks of switches by holding one of the 16 outputs low. Each switch bank will have as many as 16 switches, each wired to one of the 16 inputs. This allows for 256 switches with just two port expanders.

Initial Prototype: Two output lines with two switches wired to a single input port. The outputs have a 220 ohm resistor between the output and the switch bank. This may or may not be sufficient. There may need to be multiple resistors and other circuitry isolating the switches in the bank.

I2C

• different speeds
• Error Detection and re-transmission
• Client to ATMega
• Client to Port Expander

Client on AtMega

Communication

• I2c
• SPI
• Raw Data Protocol

Data Acquisition

• Switch
• Rotary Encoder
• Magnetic Encoder
• Potentiometer

Control Data

• Air Core
• Stepper Motor
• Lighting Level

Building

Hardware Choices

• AtMega Models
• Raspberry Pi III
• for 7 and 16 segment displays
  • Max7221
  • or 7 Segment Driver Transistors
• 4 to 16 Multiplexer
• Magnetic Encoder
• Rotary Encoder
• Slider Potentiometer:
• Power Supply: Bench Supply based on an ATX PC power supply
• Knobs
  • Heading Adjusters
  • Radio Stack Volume
  • Radio Stack Frequency Select
  • Radio Stack Buttons
  • Rotary Switches
  • Rocker Switches
  • Toggle Switches
  • Main Switches
  • Magneto Switch
  • Flaps Lever: Design the Mechanism to attach to a rotary switch