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Apr 18, 2017, 11:07 AM
AKA jflyper
Thread OP
Mini-HowTo

TRI OMNIBUS (BF3.1) Notes


Introduction

Collection of information for building tricopters with OMNIBUS family FC.

Servo Signal Mapping

OMNIBUS AIO and Pro (F3)

With OMNIBUS AIO and Pro, motor 3 (PWM3) or motor 4 (PWM4) can be assigned to a tail servo.

Code:
resource servo 1 a3 # For motor 3 (PWM3)
resource servo 1 a2 # For motor 4 (PWM4)
OMNIBUS F4 AIO and Pro

With OMNIBUS F4 family, motors 1 & 2 and 3 & 4 each shares a timer, so one of these signals can't be assigned to a tail servo.

Use motor 5 or motor 6 (labelled PWM5 and PWM6 respectively) instead.

Note that with 3.1.7 and later, LED strip signal is available at designated signal connector/through-hole, so PWM5 and PWM6 are free for use, except for OMNIBUS F4 AIO (the original F4 AIO without SDCARD) in which PWM5 is used for LED strip signal.

Code:
resource servo 1 a1 # For PWM5
resource servo 1 a8 # for PWM6
Servo Configuration and Setting

The tail servo will be automatically configured using the first (and only) servo assigned in the signal mapping section above, and it will appear as "servo 5" (zero origin) in the servo tab of the configurator.

Servo View

Signal to the tail servo can be monitored using motors tab of the configurator. "Servo 6" (one origin) is the tail servo.
If you setup the angle mode, you will be able to see the servo 6 respond to yaw movement of the tricopter.

Servo Powering

Servos are considered dirty in terms of power, and it is best to avoid powering it from where other sensitive electronics are powered, such as FC's main 5V rail. This means that it is best to use a separate external power supply to power servos.

Other tidbits

- CLI variable tri_unarmed_servo
When this variable is set to ON, the tail servo is activated even when unarmed. It is useful for testing the servo's basic functionality. However, for actual flying, it should be set to OFF. When ON and ANGLE or HORIZON mode is used, servo responds to YAW movement and it's may be annoying. Additionally if stick arming and your ESC is calibrated to start when armed, then servo will move to full left when you arm the copter, which is bit scarely.

- CLI variable servo_pwm_rate
This CLI variable determines how often control signal is updated for tail servo control.
For conventional servos, it should be untouched at 50 [update/sec] (which is default).
For digital servos, you can set it to 250~300 range [update/sec].

Faster update rate means less latency in control, but it doesn't make sense to set it too fast.
If you have a digital servo installed, you may be able to feel the difference by changing the value.

- Refernce of CLI variables
https://github.com/cleanflight/clean...er/docs/Cli.md
Last edited by teralift; Apr 18, 2017 at 12:24 PM.
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Apr 18, 2017, 11:27 AM
AKA jflyper
Thread OP

Why are servos numbered differently in different places?


In the note above, the tail servo is called in three different ways; "servo 1" in the resource command, "servo 6" in the servo tab, and "servo 5" in the motor tab.

The numbers in the servo and the motor tab are essentially the same (zero or one origin makes the difference), and it is a "servo slot" number, beginning with zero. There are eight servo slots defined, and each slot has pre-defined functions. The sixth slot (servo slot 5) is a RUDDER slot. The TRI mixer use the RUDDER slot to control yaw motions.

Used servo slots are then mapped to logical servos, numbered from one. A rule for the mapping is simple; first comes the servo slots defined by mixer, then two gimbal servos (if SERVO_TILT feature is enabled) comes next, and lastly comes RC channels directly forwarded (unprocessed) if CHANNEL_FORWARDING feature is enabled.

In our example of the simple tricopter, there is only one servo slot used (servo slot 5), and it will be mapped to logical servo 1.

Logical servos are then mapped to MCU pins by resource CLI commands.

Ref: https://github.com/cleanflight/clean.../docs/Mixer.md

Attached drawing is a more complex configuration example of tricopter + camera gimbal + 2 PWM channel forwarding, but you can see that servo slots, logical servos and physical servos are linked together using the above rules.
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Last edited by teralift; Apr 18, 2017 at 01:17 PM.
Apr 18, 2017, 12:19 PM
AKA jflyper
Thread OP
Reserved
Apr 18, 2017, 01:15 PM
AKA jflyper
Thread OP
Reserved
Jul 10, 2018, 06:21 PM
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josephr's Avatar

Omnibus Fc alternative


Hello Teralift,

I wanted to raise the question about Omnibus FC alternatives for Tricopters. The reason why I ask is that I recently purchased an Airbot Omnibus F4 V5 FC as it was becoming difficult to purchase a V3 and what I noticed is that PWM 5 and 6 pads are not as they were in the earlier versions. Having spoken to Airbot, they have commented that they will be moving away from having PWM 5 & 6 pads with future design's.

This means that I need to start looking for an alternative F4 or F7 FC which supports and has connection pads for PWM 5 & 6 for my Tricopter builds.

Do you know or have you come across other manufacturers of FC's that support PWM 5 & 6 and have connection pads that are not small exposed copper tracks on the FC's PDB.

Appreciate your comments and thoughts. Thank you, Regards, JosephR.
Jul 10, 2018, 08:01 PM
AKA jflyper
Thread OP
Quote:
Originally Posted by josephr
Hello Teralift,

I wanted to raise the question about Omnibus FC alternatives for Tricopters. The reason why I ask is that I recently purchased an Airbot Omnibus F4 V5 FC as it was becoming difficult to purchase a V3 and what I noticed is that PWM 5 and 6 pads are not as they were in the earlier versions. Having spoken to Airbot, they have commented that they will be moving away from having PWM 5 & 6 pads with future design's.

This means that I need to start looking for an alternative F4 or F7 FC which supports and has connection pads for PWM 5 & 6 for my Tricopter builds.

Do you know or have you come across other manufacturers of FC's that support PWM 5 & 6 and have connection pads that are not small exposed copper tracks on the FC's PDB.

Appreciate your comments and thoughts. Thank you, Regards, JosephR.
I would try OmniNXT line. There is an F7 variant available now, and iirc, F4 variant is coming.
Last edited by teralift; Jul 10, 2018 at 08:07 PM.
Jul 11, 2018, 06:12 PM
Registered User
josephr's Avatar
Hello Teralift,

Thank you, I have spoken to Airbot and they indicated they could supply a version of the NXT with only 1 gyro, the base gyro and that this FC supports 6 motors, have not taken them up on it yet but am considering. Only issue that I can see so for is that I have been using PPM Spektrum receivers and the NXT does not support PPM only S-Bus.

Have you been well, what are you working on these days? Regards, JosephR.
Jul 11, 2018, 07:07 PM
AKA jflyper
Thread OP
Quote:
Originally Posted by josephr
Hello Teralift,

Thank you, I have spoken to Airbot and they indicated they could supply a version of the NXT with only 1 gyro, the base gyro and that this FC supports 6 motors, have not taken them up on it yet but am considering. Only issue that I can see so for is that I have been using PPM Spektrum receivers and the NXT does not support PPM only S-Bus.

Have you been well, what are you working on these days? Regards, JosephR.
No worries, NXT architecture does support PPM input.

In fact, the NXT architecture is the most versatile and most featured pin assignment for 64-pin STM32 F4 and F7 package.

OmniNXT7, the first NXT implementation, does have PPM input configured:
Default PPM pad for OmniNXT F7 is RX1 (for BF v3.4.0, will be changed to RX2 in next patch release), but you can reassign any timer capable pad to handle PPM.

There are 6 through-hole MST (motor/servo/timer) outputs, in which M5 and M6 positions can be assigned as servos.
Aug 03, 2018, 03:46 PM
Registered User
Hi, teralift, I just got omninxtF7 and wondering if there is anything i should take care while wiring it up?Can i power the board via Vbatt and are all Uarts same?I mean i can connect anything to any UART or i should connect my receiver to UART1 only?

I found barometer on omninxtf7 is not advertised on their website but after looking ,i found that there is baro sensor which supposed to be ST LPS25HB(as per Inav status command) but the marking doesn't match with ST LPS25HB.Also inav configurator shows it as 'FAKE' on the configuration menu.
Aug 03, 2018, 08:38 PM
AKA jflyper
Thread OP
@ninja_zx11 Are you wiring OmniNXT7 for a tricopter?
Aug 03, 2018, 08:53 PM
Registered User
Quote:
Originally Posted by teralift
@ninja_zx11 Are you wiring OmniNXT7 for a tricopter?
Sorry no.I am installing it in a quad.
Aug 03, 2018, 08:59 PM
AKA jflyper
Thread OP
Yeah, we need a dedicated thread for OmniNXT boards...


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