Why do I say aftermath? Well to put it simply it might have been a bit of an overreach.  I spent more than a few days trying in vain to get the display board pins identified.  So here are some videos for the Fuel Load Indicator.  First up are the function switches.

These three images are  from  "Embed With Elliot: Debounce Your Noisy Buttons"  

There is one more board and that is the Signal Conditioner. This is a small board that connects to the switches and the Interface board. The Signal Conditioner is a  simple RC network where, T = C * R, or .001 seconds,  to get rid of the jitter or ringing.

I am using interrupts from the switches provided by an SN74LS147 which is a 7-inputs to BCD outputs that triggers the interrupt. To get the 3-bit outputs (Arduino inputs) into one integer I used the bit shifting:


void ISR_swtiches ( ) {   // Get the output from SN74LS148
  vA = 0;
  vB = 0;
  vC = 0;
  vA = digitalRead ( A0 );
  vB = digitalRead ( A1 );
  vC = digitalRead ( A2 );

int getPEoutput() {       
  int value = 0;
  int retvar;
  // if vA = 1 vB = 0 vC = 1
  // Shift the MSB first
  value = vC << 1;    // 010
  value =+ vB;        // 010
  value <<1;          // 100
  value += vA;        // 101



The displays IC are a pair of DSP-2131TXV, which are smart devices that is intended to have both an Address-bus and Data-bus that the Arduino does not have. The problem is solved by using an I2C I/O 16-bit expander. The MCP 23017 can be used as two separate 8-bit registers, which become my two buses.

One of the problems that I have is that the Display Board is bolted into the housing. At which point the Interface board plugs into the Display board. The problem is getting them apart (it's a pain). You have to unmount the Display board from the housing. So that means I have to trim the Interface board so that I can get to the four screws in the bottom of the housing.


AFTERTHOUGHTS: Having problems with Arduino's CAN implementation. I have decided to sort of roll my own interface based loosely on  CANopen which is a superset of CAN and very closely related to CANaerospace itself. But for testing USB will work fine. I have a crude program on my PC which can send and receive frames.

CANopen-Slave on git




Now here is some WireWrap on the custom interface board.

Componentes on the Interface board.