I recently bought a miniature ASK transmitter and receiver, STX882 and SRX882 (both on 315MHz), with the intended use of making a wireless ground station for my long range FPV drone. The aim is to create a wireless link between my FUTABA radio control and my EzUHF long range transmitter. The signal that the Futaba Radio is putting out through the trainer port is a PPM signal. This PPM signal is actually a combination of 8 PWM signals corresponding to the 8 channes on the receiver. This PPM sigmal is therefore and analog signal due to the fact that each channel duration corresponds to an encoder position of the servos and the speed control.
From the beginning it did not work. I was trying all kinds of things to fix the error but there was no other way than to debug with an oscilloscope. As you may be able to see in the attached pictures, the top curve on the oscilloscope (yellow) is the PPM signal before it enters the transmitter and the bottom curve is the received signal after demodulation. There is a visible prolonging in the duration on each channel and this causes the EzUHF not to recognize the 8 channel signal and hence will not transmit the data.
If you follow to look at the images, you will be able to see that there is a voltage increase after each channel segment on the input side and what i'm guessing is happening is that the demodulator on the receiver thinks that that increase is like an AC signal and therefore simply adds it to the previous channel signal.
Also, as soon as I disconnect one of the three wires of the transmitter, the PPM signal is restored back to normal immeadiatly so the conlusion is that the STX882 is responsible for this mistake in transmission.
Can anybody help me with this, does anyone know how to fix this issue?
PS: When I hold the transmitter in a particular way (the left and right side, perpendicular to the pin connections), this increased spot seems to shorten.
From the beginning it did not work. I was trying all kinds of things to fix the error but there was no other way than to debug with an oscilloscope. As you may be able to see in the attached pictures, the top curve on the oscilloscope (yellow) is the PPM signal before it enters the transmitter and the bottom curve is the received signal after demodulation. There is a visible prolonging in the duration on each channel and this causes the EzUHF not to recognize the 8 channel signal and hence will not transmit the data.
If you follow to look at the images, you will be able to see that there is a voltage increase after each channel segment on the input side and what i'm guessing is happening is that the demodulator on the receiver thinks that that increase is like an AC signal and therefore simply adds it to the previous channel signal.
Also, as soon as I disconnect one of the three wires of the transmitter, the PPM signal is restored back to normal immeadiatly so the conlusion is that the STX882 is responsible for this mistake in transmission.
Can anybody help me with this, does anyone know how to fix this issue?
PS: When I hold the transmitter in a particular way (the left and right side, perpendicular to the pin connections), this increased spot seems to shorten.
