01-Nov-2018, 12:47 PM (This post was last modified: 01-Nov-2018, 06:32 PM by hawkwadfpv.)
Some days ago I received my new R9MM 900MHz receiver and I decided I would flash it with the flex firmware and use FPort as the RX protocol so that I could run SBus and Telemetry on the same wire. After a few of trials and errors I ended up wiring the FPort cable on TX3 on my Omnibus F4 V3 flight controller. I moved the VTx telemetry wire, that was connected to the TX3, to the TX6 but since then VTx telemetry stopped working... I tried moving it to the TX1 but had no results, I also tried messing up with softserials but it didn't work either, any idea?
EDIT:
This is part of my BF config, I'm running BF4.0 (but it wasn't working on 3.5.2 either)
# serial
serial 20 1 115200 57600 0 115200
serial 0 0 115200 57600 0 115200
serial 2 64 115200 57600 0 115200
serial 5 8192 115200 57600 0 115200
# get serial
serialrx_provider = FPORT
Allowed values: SPEK1024, SPEK2048, SBUS, SUMD, SUMH, XB-B, XB-B-RJ01, IBUS, JETIEXBUS, CRSF, SRXL, CUSTOM, FPORT
Default value: SPEK1024
serialrx_inverted = ON
Allowed values: OFF, ON
Default value: OFF
serialrx_halfduplex = ON
Allowed values: OFF, ON
Default value: OFF
serial_update_rate_hz = 100
Allowed range: 100 - 2000
EDIT2: Added picture of wiring. The red-circled white wire is the FPort wire (connected to TX3). The green-circled white wire is IRC Tramp telemetry wire (connected to softserial 1, led_strip port).
EDIT:
This is part of my BF config, I'm running BF4.0 (but it wasn't working on 3.5.2 either)
# serial
serial 20 1 115200 57600 0 115200
serial 0 0 115200 57600 0 115200
serial 2 64 115200 57600 0 115200
serial 5 8192 115200 57600 0 115200
# get serial
serialrx_provider = FPORT
Allowed values: SPEK1024, SPEK2048, SBUS, SUMD, SUMH, XB-B, XB-B-RJ01, IBUS, JETIEXBUS, CRSF, SRXL, CUSTOM, FPORT
Default value: SPEK1024
serialrx_inverted = ON
Allowed values: OFF, ON
Default value: OFF
serialrx_halfduplex = ON
Allowed values: OFF, ON
Default value: OFF
serial_update_rate_hz = 100
Allowed range: 100 - 2000
EDIT2: Added picture of wiring. The red-circled white wire is the FPort wire (connected to TX3). The green-circled white wire is IRC Tramp telemetry wire (connected to softserial 1, led_strip port).
Hojo and the case of the deaf Tentec Omni V
A friend from the local ham club handed me his Tentec Omni V. He hadn't used it in a while, and was preparing to sell it to another ham when he noticed it appeared to be very weak on receive. He asked me to take a look.
Omnibus F4 V2 Pro Pinout
Lennukontrolleri Omnibus F4 juhend - Omnibuse F4 lennukontroller juhend on kirjutatud spetsiaalselt Omnibus F4 V3 jaoks ja vanematele. HAKRC Omnibus F4 V3 Flight Controller OSD w/ 5V 3A Power Distribution Board for RC Drone FPV Racing. Specification: Brand name: HAKRC Item name: Omnibus F4 V3 Flight Controller + PDB. Flight controller Firmware: inav1.9.0OMNIBUSF4V3.hex MCU: 168MHz STM32F405 External IMU: ICM20608(The default IMU is ICM20608, you can also choose MPU6000) Baro. Resource Remapping is an awesome feature in Betaflight, that allows you to swap some pins around on a flight controller. Using Resource Remapping there are so much you can do, for example, to change motor ordering, relocate pins in case of ripped-off solder pads, and many more!
Power supply
Right off the bat, I checked the power supply. It was reading low. The trimmer pot was right next to the activity LED, so I couldn't resist dialing it up to a proper voltage.
Initial problems
I powered up the rig and found the LED display blank. I opened the covers and wiggled a few things directly behind the LED display. It flashed back on. The board was not seated very well, apparently.At the same time, one of two incandescent bulbs behind the S-meter was intermittent. I snugged up the fixture with a pair of pliers, and the bulb became more reliable.
Having taken care of those little physical problems, I could finally try injecting a signal into the radio. Sure enough, it was quite hard of hearing. I needed a signal of about -20 dbm to be discernible. I confirmed the problem existed across multiple bands.
Diagnostics
I opened up the radio and started tracing the signal. I injected a tone on 14 Mhz (1) and followed the path. It got through the antenna selection circuits and initial attenuator just fine. It reached the front-end mixer board (2), and exited that board mixed to 9 Mhz (3). I also verified that the signal disappeared when the injected signal was stopped. So far so good. The signal passed through the 9 MHZ IF board (3) -> (4) unmolested and was amplified slightly. From there, it went into the Pass Band Tuning board (4), and finally into the AF/IF board (5). There's where the trouble began.I measured a good signal coming into the board (5 above). It passes through a few amplifier stages first thing. I checked at the end of that stage and found no signal. Tracing back, I found the signal disappeared after passing through a J310 Fet.
I next confirmed that there was power on the '+REG' rail. It was reading 8.78 volts. Unfortunately, I had no idea what the voltage was supposed to be. After about 40 minutes of tracing the +REG rail back to a power board, I found a knockoff sentence in the service manual that +REG should be 8.5 volts. So, it was a touch high, but shouldn't have been a problem for this situation.
Having narrowed it down to this Fet, I checked my parts bin, and voila, I had a few in stock!
The repair
Omnibus F4 Pro Pinout
Testing
After putting things back together, the radio was hearing loud and clear. My Service Monitor can generate signals as low as -130 DBM. The signal was clearly discernible all the way down.Talking with the owner, he was satisfied that the repair was sufficient, so I stopped there, rather than attempting to find alignment instructions.
Success!