Omnibus F4 Pinout

Omnibus F4 is a new family of All-In-One (AIO) STM32F4 based flight controllers with integrated OSD (On-Screen-Display) for FPV purposes. Basically, it is Airbot F4 / Flip32 F4 with added MAX7456 and some minor tweaks.

• OSD connected via SPI bus
• VCP port
• 3 UART ports, UART3 is shared with I2C
• Hardware inverter on UART1 allows to connect S.Bus receivers
• Dedicated PPM/S.Bus connector
• DSMX connecter
• PWM connector that allows to connect 4 PWM channels
• Integrated voltage stabilizer and voltage monitoring
• Analog current monitoring
• Analog RSSI monitoring
• Buzzer connector
• Integrated 16MB Blackbox flash memory

Currently, only Betaflight and Raceflight (?) supports OSD on this board. INAV OSD support is on its way.

Notes:

• RAM pins are connected only to each other. For OSD only GND and Video IN and Video OUT lines have to be connected with camera and VTX
• Integrated voltage stabilizer tends to get hot when powered from 4S. Do not try to power camera or VTX from it
• Current and RSSI are NOT 5V tolerant. 3.3V max
• S.Bus and DSMX are shared with UART1
• To use UART1 and PPM, SBUS jumper has to be removed

Omnibus F4 can be purchased as Airbot Omnibus F4, Flip32 F4 Omnibus and "no-name" from Banggood and other Chinese shops.

FrSky X12S Horus spotted in the wild

Last weekend I had a brief opportunity to take a look at new radio from FrSky: X12S Horus. One thing is sure, this thing is quite impressive. For me it is slightly too big and too expensive. Plain old Taranis suits all my needs. Owner seems too be quite happy with his X12S Horus, and here are his main thought about it:

• Big and heavy with a stiff frame. As long as you do not have to carry it attached to your neck for a longer period of time, it is completely fine
• LCD screen is nicely visible in daylight
• Nice Hall effect gimbals!
• Rubber bumpers allows to put Horus on a car's roof or hood without the risk of scratching it
• Shipped with FrSky software, that is not as good as OpenTx
• External antenna connector with a VSWR

MPU6000 vs MPU6050 vs MPU6500

MPU6000 and MPU6050

Deep down, MPU6000 and MPU6050 are the same same hardware. They both have the same 3 axis gyroscope and the same 3 axis accelerometer. Both allows max 8kHz gyro sampling rate. From a flight controllers point of view, the only difference between them is bus that connects them to CPU. MPU6000 allows for both I2C and SPI, while MPU6050 has only I2C. That makes MPU6000 better device, but only when SPI bus is in use. I2C is too slow to handle 8kHz gyro updates.

MPU6500

No, MPU6500 is a different monster. It supports both I2C and SPI, allows 32kHz gyro update rate and has much wider gyro signal bandwidth. Is also smaller and consumes less energy. So, in theory, it is much better device than MPU6000. There are some problems with it. First of all, it is much more vibration sensitive than MPU6000. While soft mounting of MPU6000 is usually not needed, MPU6500 will benefit a lot from it. Very often it is even required. Second of all, at this moment, only RaceFlight can utilize 32kHz gyro update rates.

MPU9150 and MPU9250

What are those two MPUs? It's rather simple this time.

• MPU9150 is a MPU6050 with integrated AK8975 magnetometer
• MPU9250 is a MPU6500 with integrated AK8963 magnetometer

Images: 1 2

UART1 and PPM on Airbot F4 / Flip32 F4 Flight Controllers

Today I've discovered another small but irritation limitation of Airbot F4 / Flip32 F4 also known as CC3D REVO for unknown reason. Looks like, by default, this board is unable to share UART1 RX line and PPM input. So, if you would like to connect, for example, OSD or GPS to UART1, you would have a problem. I've discovered that PPM input does not blocks UART1 totally, but makes UART1 transmission erratic and unreliable.

This is because PPM input pin is connected to both UART1 RX (pin PA10 of STM32F405) via inverter and PPM input pin (PB14) without inverter. Any electrical signal applied to PPM input would also be sent to UART1 RX.

Luckily, there is pretty simple, hardware, solution to allow UART1 and PPM input function simultaneously. Jumper called SBUS located near SBUS/PPM input has to be removed with soldering iron. This operation breaks the connection between PPM/SBUS input and UART1 RX.

There is a drawback of this solution too. If jumper is removed, SBUS will not work. To make SBUS works again, jumper would has to be closed again. With a blob of solder for example...

Singles' Day Deals for DJI Phantom

In some countries 11.11 is an Independence Day. In some countries it's a shopping festival. If anyone want's to cut a good deal, this is one of the best times to do it. For example on GearBest which prepared very nice promotions for DJI Phantom series.

• DJI Phantom 3 Advanced for $580,99 (original price $799) with a coupon GBDJ3A
• DJI Phantom 3 Professional for $725.99 (original price $999) with a coupon GBDJ3P
• DJI Phantom 4 for $999.99 (original price $1199) with a coupon GBDJ4

How much power flight controller consumes?

Year after year flight controllers grow stronger, faster, more powerful. Three years ago we had MultiWii running Arduino. Two years ago it was Naze32 with STM32F1. Year ago it was SPRacingF3 with SMT32F3. This year it is something with STM32F4. Is there a price is power consumption to pay? Should we start using stronger BECs? 1A? 2A or maybe 3 amps are now required? I've decided to check.

Measured current required by flight controllers I had on hand:

• Flip32+ 7DOF (special version of 10DOF without magnetometer): 44mA
• SPRacingF3 Acro (chinese clone): 55mA
• Airbot F4 / Flip32 F4: 93mA

So, there is a price to pay in terms of power consumption. But, let's be honest here. Even increase by more than 100% when going from F1 to F4 is not putting much drain on any decent BEC. Good and solid 1A BEC should be more than enough to power most setups.

INAV 1.3 has been released

I'm happy to announce new version of INAV ready do download from official repository.

What is new in INAV 1.3? Quite a few thinks. No "revolutions", more like steady progress. From most important things:

• INAV now supports PWM, OneShot124, OneShot42 and Multishot ESC protocols and asynchronous motors and servos updates
• Something for airplanes with a lot of servos: INAV can now supports PCA9685 PWM drivers and drive up to 16 servos plus motors! Although mixer can not yet support as many servos, this will change in future releases. I will try to write few words on this topic in a near future
• FlySky I-Bus telemetry
• Airplane auto arming with throttle option
• In case of airplanes (again airplane improvement!), I-term of PID controller is constrained to about 30% of max servo throw. This prevents from servo saturation that can happen in some cases before take off
• I2C improvements for STM32F1 and STM32F4 targets. This solves the problem of undetected BMP085, BMP180 and HMC5883L on Naze32, Flip32, OpenPilot Revolution and other boards
• Code cleanups, including removal of unused or very rarely used flight modes like SERVO1-3, GOVERNOR, LEDMAX and CAMTRIG

All users are advised to use latest INAV Configurator and reconfigure flight modes is configuration is to be restored from files! Owners or STM32F1 boards should consult hardware support map if features they are using are still supported.

Flip32 F4: what is where

PWM, OneShot125 and Brushed motor protocol on an oscilloscope

When I've buoght an oscilloscope (cheap digital DSO201), I've decided it would be a good idea to see how different ESC protocols looks like from the signal point of view. Previously I've written few words about them, like which is the fastest as so on, but is there something "special" about them?

Well, let's find out...

"Standard" PWM at 400Hz

0% throttle

100% throttle

OneShot125 at 1kHz

0% throttle

100% throttle

"Analog" PWM used in Brushed motors at 16kHz

0% throttle

100% throttle

Summary

Well, looks like PWM, OneShot125, OneShot42 and Multishot (no screenshots for last two, but they are so similar it just made no sense to post those) are basically only an variation of the same basic idea: throttle position is encoded as a period of time between rising and falling edge of a signal. 0% throttle is encoded as period A, 100% as period B. Everything between is scaled lineary. Protocols differ only in update frequency and period lengths for 0% and 100% throttle. Boring...

Only "Analog" PWM for brushed motors is different. There are not rising edges on 0% and throttle, since 0% throttle means no current on motors.

But, this can change. There are first attempts for digital ESC protocols. Betaflight is preparing for DSHOT600 and DSHOT150 digital protocols as I write. Like always, hardware support is/will be highly limited, but hmm... ESC telemetry? Why not...

Project Dualcopter - worklog #2

3 weeks after my first post on Project Dualcopter, it's time for small update. The plan was to install servos and control surfaces. Instead, I've done:

• Basic electrical wiring for motors and ESCs. They have power now and are ready to be connected to flight controller
• To level shelf (above propellers) designed to hold flight controller and radio receiver
• Think for a moment about landing gear. Yeap, there will be some sort of shock absorbers
• Think for a moment where battery will be placed: as low as possible to keep center of gravity below center of thrust
• Decide which propeller should run clockwise and which should run counterclockwise: top should go clockwise, bottom should go counterclockwise