A few people have been asking me what the difference between PPM and SBUS is, and which type of receiver they should use.
Both PPM and SBUS connect to your receiver easily with one servo connector as shown below:
The short answer - SBUS is better
Here are the main reasons why SBUS is better.
- SBUS is better as it is faster (lower latency)
- SBUS is a digital signal so it has higher resolution which means you have more precise control over your aircraft.
Should I upgrade from PPM to SBUS?
If you are planning to buy a new receiver, its probably worth getting one that has SBUS functionality, but for 99% of pilots you will probably not notice any difference so its not necessary to upgrade from PPM.
SBUS inverter
FRsky Sbus receivers use an inverted SBUS signal, so depending on what flight controller you are using you might need to use an SBUS inverter cable between your R/C receiver and flight controller. Most flight controller documentation will let you know if this is needed, but the most common time to use this is if you are using a nase32 Rev5 board or earlier.
You can either buy an SBUS inverter cable, or make your own using an 2N7002E mostfet inverter and some resisters.
Error Handling
Because PPM is an older analogue signal, there is not built in error checking so the receiver will use a moving average to smooth out any possible spikes in the signal due to interference.
This smoothing unfortunately introduces an extra delay which increases the latency of the PPM signal. In reality this latency is around 60ms, compared to about 20ms of SBUS. In most applications this does not realy matter, but when it comes to miniquad racing at high speeds a delays of 50ms can result in about 1.4 meters of travel if your aircraft speed is 100Km/h
In contrast since SBUS is a digital signal, calculations such as parity bits can be included with the signal to correct for any possible interference which keeps the latency to a minimum.
To learn more check out our guide on types of R/C protocols