I did place some info in the 7PX topic about different modes but it fits here as well.....
I was busy with some receivers and measured the framerates of several modes and options.
I made a list:
I know some people do care more about latency so let me explain.
There are 3 types of latency. (for those who do not know what latency is, it is the time difference from changing control on the input to the reaction on the output)
1) A steady but small latency time is by the speed of electronics and processor handeling. This one is easy to get used by the mind because it is a steady factor. It could be measured. by modifying the transmitter to let it controlled by a computer and an electronic sensor on a channel and measure the time difference of a change.
2) A non steady and very unpredictable time by interference which is not easy to measure. You need to setup a device to simulate all kinds of interference. This is related to like high voltage cables under/over the track, the mirror signal from a fence but also other devices where the receiver need to correct or re-read the signal.
3) Frame rate.
Sensing all channels within the transmitter is like a train running circles and over the whole round all channels as like train stations are located. In the servo with a 1.5ms center pulse width the move will start after it reads and decoded the pulse width. It depends where the train is when you change a channel value. If you have an old system with a 20ms framerate the latency can be 1.5ms (if the train is excact on time) up to 20ms (when the train just drove by and need to make an whole 20ms round). On a RC track with fast cars taking a corner that can be a difference of getting the apex right, getting launched over the curb or going one meter too wide. The faster the framerate is set, the smaller this variable and so more steady this factor will become. Lowering the center pulse width is also a thing to lower the steady latency, that is why Sanwa its SSR went to 300uS pulse width but it is also needed when you want higher framerates beyond 333Hz.
What do we see in the list......- SR is damn fast
- The T-FHSS mode is faster compared with T-FHSS-SR with normal digital servo's, so when using normal digital servo's do not use the T-FHSS-SR mode.
- SBUS is slow, most Futaba SR servo's can work over SBUS but why would you do that?
- Even the cheaper S-FHSS receiver set to digital servo's is decent fast. (close the old Futaba 3PK HRS system)
- For those who are into RC helicopters must recognize the SR 760us servo signal. Many tail servo's connected to a gyro do use this so called small band signal. Sad enough most of them go up to 500Hz but there are 800Hz tail servo's to be found.
- It seems telemetry has no influence on the speed.
I also opened a R203GF and a R304SB receiver to replace the antenna wire, of the R304SB it was a bit damaged and on the R203GF I wanted to make it an E-version with a short antenna. On the R304 the antenna is plugged onto a PCB connector, so very easy to replace, sadly on the R203 it was soldered and then covered with some kit. But then I came to the idea to find out the real voltage range by looking up the specs of the voltage regulator (upper left corner on the pic below) because it is a common question where the 7.4v as a maximum is always a discussion if it is OK with an 8.4v 2S lipo. Keep in mind the 7.4v notation is a nominal voltage for a 2S LiPo.
A chip with code 9XZ is used, only with a different last code. After some searching to the type SMD housing and SMD code I came to the XC6209 voltage regulator. The chip code is 9X, the Z stands for a 3 volt version and the last code is a production code.
The chip can handle up to 10 volt specified! And it even has a 12v maximum rating which is not wise to use it.
Another funny thing on this picture is a non used 4th channel. This is the 3 channel R203FG receiver but the whole layout (led and bind switch) looks similar with the 4 channel R2104GF and all components to the signal pin are on the circuit board. Put the scope on it and yes, it is a full functional channel 4!