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Mapping of EXBus (12-bit) and SBUS (11-bit) to PWM pulse length with Jeti

  • nickthenorse
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Mapping of EXBus (12-bit) and SBUS (11-bit) to PWM pulse length with Jeti

04 Juli 2024 16:16 - 04 Juli 2024 16:20
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Hi!

As far as I am aware, the ExBus protocol operates with channel information in 12-bit (4096 positions) and SBUS is per specification 11-bit (2048 positions).

Also, as far as I can tell, the default pwm pulse widths for Jeti are:

100 % servo travel = 1000us -> 1500us -> 2000 us
150 % servo travel = 750us -> 1500us -> 2250 us

Does anyone know if the ExBus resolution of 4096 steps is allocated to the full 150 % travel range? Which means (2250us - 750us) / 4096, or 0.366us per step.

What happens with the SBUS signal? A min of 750us and a max of 2250us is outside the valid range for the SBUS protocol, I believe. What range do Jeti receivers map the stick input range to? (Or I suppose with the SBUS output from a REX, it simply outputs a signal between 0 - 2047, and lets the flight controller downstream do the SBUS -> PWM mapping).

Thanks!
Letzte Änderung: 04 Juli 2024 16:20 von nickthenorse.

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  • nichtgedacht
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Re: Mapping of EXBus (12-bit) and SBUS (11-bit) to PWM pulse length with Jeti

13 Juli 2024 12:39
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nickthenorse wrote:
Hi!

As far as I am aware, the ExBus protocol operates with channel information in 12-bit (4096 positions) and SBUS is per specification 11-bit (2048 positions).

Also, as far as I can tell, the default pwm pulse widths for Jeti are:

100 % servo travel = 1000us -> 1500us -> 2000 us
150 % servo travel = 750us -> 1500us -> 2250 us

Does anyone know if the ExBus resolution of 4096 steps is allocated to the full 150 % travel range? Which means (2250us - 750us) / 4096, or 0.366us per step.

What happens with the SBUS signal? A min of 750us and a max of 2250us is outside the valid range for the SBUS protocol, I believe. What range do Jeti receivers map the stick input range to? (Or I suppose with the SBUS output from a REX, it simply outputs a signal between 0 - 2047, and lets the flight controller downstream do the SBUS -> PWM mapping).

Thanks!

With the EX-BUS, the values for the channels are transmitted in microseconds (the actual servo signal). More precisely, it is micro seconds × 8, which means that EX bus value >> 3 = value in micro seconds. I don't know how far the actual resolution extends below 1 micro second. In UDI (SRXL) there are 4096 states (values) for the entire range (including servo values < 1ms and > 2ms) In S-Bus there are 2048 states

Gruß Dieter

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