An introductory blog on hooking up the Omnibus F4 + OSD Flight controller available at PhaserFPV. Thanks to Mick Ward for sharing his findings on the ins and outs of this FC.
The Omnibus F4 + OSD flight controller is an F4 flight controller that combines betaflights OSD which can be managed inside Betaflight itself, with a number of other functions and parameter adjustments available compared to the F3 + OSD boards.
It is capable of 8k/8k loop times with ease and incorporates the MPU 6000 low noise gyro which is superior in many ways to the 6050 and 6500 used in past FCs.
It also has a linear 5v regulator on board so the FC can be powered by mains. It is not without some limitations however. It would seem that if the 5v rail gets overburdened the FC can brown out or reset or perhaps in the worst cases blow the 5v reg. The 5v linear reg is rated for 1.5A but the closer you get to this limit the hotter it gets. Also the higher input voltage the greater the losses to heat. Basic testing has shown that if the FC is hooked up to VCC (mains power, in this case a 4s battery) and is only powering the FC + OSD and receiver then it is fine.
If you decide to power a string of LEDs and your camera or other accessories off the FCs 5v rail you may find it struggles to cope. But there is a simple workaround.
Firstly lets look at the schematic:
This pinout is for the F4 +_OSD but closely resembles the Pro version as well. On the right hand side you can see 5 x 3 pin holes which are our motor pins (J14 to J12) and Uart 1 SBUS/PPM connection (J7). Above that you can see the OSD connection pins. If you want to run an OSD you would take your cameras video out and ground wires and run them to the first AGND and VIN pins. Then take your VTX Gnd and Video in wires and run them to AGND and VOUT. The RAM pins do nothing unless you configure them to output 5v, which is not recommended for the reason discussed above, and also because if your voltage slumps below 5v it can lead to your camera dropping out. Its for this reason (and to reduce load on the linear reg) that we recommend you send 12v regulated to the camera and vtx.
On the left hand side You can see our Gnd and Vbat pins, just below the buzzer pins marked J5/J4. Connect your VCC (direct lipo connection) to the Vbat pins, taking note of the correct polarity.
These connections will be enough to get you into the air, once you have set up all your particulars in Betaflight.
If you want to run more devices off 5v you have a couple of choices, but first and foremost you need your vbat connection for measuring voltage in Betaflight. So to continue using vbat for this without overheating your 5v reg you can remove the reg and power the FC from an external 5v regulator via the motor pins in the traditional fashion.
You can locate the linear reg on the underside of the FC here.
Depending on what equipment you have on hand you have a couple of choices. If you have a heat gun you can heat the chip up until it falls off. For those who dont have a heat gun this method works well too. Using a set of sharp snips cut the two bottom legs away from the chip.
With a clean hot iron tin the top of the IC with a little solder. When the reg accepts the solder on its topside it will be hot enough to slide it off. It may seem silly but to get solder off a component/board it is often easier to add solder first. Careful not to smear the solder over other components or short any traces on the way off. Dont overheat the board. If it doesnt take solder within 5 seconds your iron is too dirty/cold or poorly placed.
If there is enough interest Phaser will offer this removal service for customers who choose it and dont feel confident in removing it themselves.
Once this chip is removed you can run wires to vbat for voltage monitoring but you must also run an external 5v source to the FC via the 5v rail near the motor pins.
Smart Audio VTX and Smart Port hookup.
Please note, an inversion hack will be needed to use smartport telemetry on this FC. You need to solder the smartport wire to the green arrow seen below.
Happy 8k/8k flying.