PCM bits and pieces?

[Rox]

I am looking for PCM details for Futaba and JR, both 1024 and 2048. I have searched but not able to find a detailed reference.

How it is possible with PCM to encode 14 10-bit channels in less than 20 ms frame? Futaba also claims to reduce the frame rate by 40% for PCM G3 2048!

[pmackenzie]

Some details worked out for Futaba 1024:
http://autopilot.sourceforge.net/pcm.html

Pat MacKenzie

[vintage1]

Delta modulation would seem to be the key. Relying on the fact that most servos stay where they are, and few move that rapidly. You exchange accuracy for response speed

[FredericG]

Some pointers here:
http://www.rc-flight.be/electronics.html

Frederic

[vintage1]

less pointers than a full blown reverse engineers guide..

Nicely engineered..they thought of most things.

[pmackenzie]

Anything out there for JR?

Pat MacKenzie

[Rox]

Frederic

Its really a nice effort and quite good information... thanks. Any information available for Futaba 2048 PCM?

I am disappointed by the data rate of Futaba PCM1024 since the latency is 28.5 msec which is worst than PPM of 20 msec and an update of difference for half of the channels for one frame. I a wondering why the data rate is only 6.67 kbps (190b/28.5ms) while the new designs have much higher data rates e.g. 32 or 64 kbps!!!