RC PPM input not working

FIZZY

Member
I am trying to receive a crossfire RC PPM signal with my teensy 4.1 but am having problems. I am using a TXS0108E Logic Level converter between the RC recever and the Teensy 4.1. I am trying to use the PulsePosition library to receive this input but It is just not working. My simple test sketch is:

Code:
#include <PulsePosition.h>

#define rxPin 6
PulsePositionInput crossfire;

void setup() {
  Serial.begin(9600);
  crossfire.begin(rxPin); 
  
  
}

void loop() {
Serial.println(crossfire.read(1));
}

this is the output from the serial monitor, it is just flipping between the two different numbers no matter what I change with the RC transmitter sticks.

Code:
748.19
0.53
0.51
1748.16
0.51
0.51
1748.16
0.51
0.51
0.51
1748.16
1748.16
1748.16
1748.16
0.51
1748.16
1748.16
1748.16
1748.16
1748.16
1748.16
0.51
1748.16
1748.16
1748.16
1748.19
1748.16
1748.19

Any help would be great! Thank you
 
I googled for "crossfire RC receiver" and got many hits.
Do you happen to have a datasheet of the exact part you are using?

Paul
 
You might want to verify that the OE pin on the TXS0108E is pulled high to enable the part. Looks like it could be reading floating bits.
 
Do I understand correctly that the receiver only has a single pin for RX, being pin CH 7?

Capture.PNG

It may be interesting to see how you actually hooked up the receiver and the TXS0108E part.
KenHahn is right that the OE pin should be pulled high.

Paul
 
Thank you for the reply! I did pull that pin high so it should have been working. But I decided to measure the voltage of the output signal of the PPM stream from the RC receiver. It was just being 2.3 volts, so I decided to just plug it directly into the teensy. It is now reading the data perfectly and everything is working great!
 
Do I understand correctly that the receiver only has a single pin for RX, being pin CH 7?

View attachment 27187

hmm, that is a bit confusing. All 8 pins are definitely outputs, so I don't quite know what that photo is showing tbh. But as I posted in my reply to KenHahn I got it to work without the logic level shifter!
 
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