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  • Author Author: phoenixcomm
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NexGen: Fuel Load Indicator: Aftermath!

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

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.

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BEFORE RC Circuit

   

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.