Where to start with this build? A lot of questions! Let's have a list of components that I have and the questions all relate to how best to combine them.
cncdrones V2 Canage 3.5 by Sub250gFPV
Flywoo GOKU GN F745 EVO HD 2-6S 20x20 AIO Flight Controller w/ 40A 32Bit 4in1 ESC
BROTHERHOBBY VY 1504.5 3950KV MOTOR
Walksnail Avatar HD Nano kit V3
Radiomaster ELRS RP3
beeper, caps, props

Aye Carrumba! I don't think that diagram is legible... moving on. I have a lot of choices to make.

Let's start with the Walksnail VTX. I know it can draw at least 1A maybe slightly more. CaddX and the reviews I've seen don't give me a number but it is probably between 1 and 1.5A. The 5V pad is rated for 1.5A and the 9V pad is rated for 2A. I would like to use the 5 or 9V pad so that the VTX won't power up when connected to my computer via USB. This is my first HD set up and the camera is powered from the VTX so please advise, 5 or 9v for the Walksnail system?
The Walksnail manual has me entering CLI commands for the VTX in Betaflight 4.4:
"set osd_displayport_device = MSP"
"set vcd_video_system = HD"
"save"
Is this really necessary? Can't I just select "HD" for Video Format in the OSD page in Betaflight? I know to select MSP for the correct VTX UART.

Next: The GOKU pad diagram recommends different UART's for different applications. I don't know if I should pay any attention to this because I can pick any UART to do anything in Betaflight. I am guessing they make pad recommendations just to group different component connections, like a GPS, or bluetooth module, in one place?

I want to have a nice loud beeper attached to the board. I am unfamiliar with how to use these GOKU pad markings: +5V, GND, LED, BB- should I connect my beeper to the +5V and GND pads? What is BB- ? I have simple beepers with just two wire connection to the FC.

The last big decision would be how to mount the VTX. In this quad the VTX will be mounted under the top plate above the FC. The battery is top mounted so the strap will pass between the VTX and the top plate. I think I should position the Walksnail VTX with its cooling fins up and as low as possible (using standoffs) to allow air to pass between the VTX fins and the strap. If I flip it over the cooling fins would be more open to airflow but the strap will rub against the wires coming out of the VTX when I change batteries. I am also planning to hard mount the VTX, no rubber grommets. Does this sound correct?

Thanks!

Hi Husafreak,

From what I can tell, the top plate on some of those frames have mount holes
(probably 20x20) for mounting an HD module. If your frame does not have
this mounting option, then make a small adapter plate. Although any material
will work, I would probably use 1/16" thick LEXAN plastic which is crystal clear
and easy to cut and drill.  

With any thing that mounts to the underside of the top deck plate, spacers
might be needed to allow clearance for the battery strap.

Later, iFly  

Which Walksnail vtx did you get, one with input voltage of 6V-25.2V?

from flywoo's page:

Quote:https://flywoo.net/products/goku-hd745-e...-plus-play
HD745EVO BLHELI32 40A
Specification: 
MCU: STM32F745 32-bit processor,216MHz, 512Kbytes Flash
IMU: MPU6000 (SPI)
Barometer: BMP280
Onboard LED：WS2812*4
USB VCP Driver (all UARTs usable simultaneously; USB does not take up a UART)
7 hardware UARTS (UART1,2,3,4,5,6,7)
Supports serial receivers (SBUS, iBus, Spektrum, Crossfire) only.
PPM and PWM receivers are not supported.
Onbord 8Mbytes for Blackbox logging
9V Power Out: 1.5A max（3S voltage input）
5V Power Out: 2.0A max
3.3V Power Out: 0.5A max
Dimensions: 41x32mm
Mounting Holes: Standard 20mm square to center of holes 
Weight: 8.5g

Built-in 40A BL_32 4in1 ESC
Support BLheli / BLHELI_32
Support PWM, Oneshot125, Oneshot42, Multishot, Dshot150, Dshot300, Dshot600,Dshot1200
Input Voltage: 2-6S Lipo
Continuous Current: 40A
Firmware: BLHELI_32

...you should be ok...

fwiw, their pic:


if resized, it's here ---> (https://img-va.myshopline.com/image/stor...048&h=1689)

@iFly4rotors Yes the top plate has 20x20 and 25.5x25.5 holes. The 20x20 holes are slotted and would have to be drilled out for 3mm screws so it'll be cleaner and easier to use the 2mm 25.5 ones. I still wonder if it should be hard or soft mounted. The more I think about it the orientation of the VTX should be fins up. It's not the best for airflow but it is better for protecting the wiring and antenna connections on the bottom. That could be a good first try for me to design a 3D print, a simple rectangle with 25.5 x 25.5 holes and a slot across the top to capture a strap and isolate it from the VTX...

@skywanderer Thank you for reproducing the diagram in a legible format! The HD Nano kit V3 is 3.1-13V input so I could use either the 5 or 9V supply. I'm using a 4s flight pack so I cannot power directly from the battery. In Oscar Liang's review he talks about the higher input voltage capability and higher power output in the same paragraph but doesn't correlate them. He says the heatsink housing allows the VTX to put out 500mW but I don't know if that is dependent on the input voltage.

Any idea what that BB- pad for the Buzzer is?

BB- and +5V for buzzer, +5v, GND, and LED for signal if using LEDs.

Should have known... Oscar did a tute for setup:

https://oscarliang.com/setup-avatar-fpv-system/

...scroll down to “Connecting Air Unit to FC”

If you are using a BEC / voltage regulator to power the Air Unit, make sure it can supply enough current. Max power consumption of the VTX is roughly 4.5W at 1200mW, the current requirement changes under different input voltage:

9V => 0.50A
12V => 0.38A
16V=> 0.29A

You could grab a 3V bec from vbat to power the vtx if concerned.

edit to add:
OH sweet, you should be able to use the 2A 5V connection if needed then.

This: "BB- and +5V for buzzer, +5v, GND, and LED for signal if using LEDs." Thank You!

It's funny (but sad) that I have read OL's article you linked a few times! The more I learn the more I can learn... As you edited though I have a different VTX. OL didn't do the same testing on the Nano V3. Interesting that the Amps go down as the voltage goes up. Something we all know but then I didn't apply it. So the VTX will draw more amps at 5V than at 9V to make 500mW max output, and the FC can deliver more amps at 5V than 9V. But since the amps are way less than needed even with the bigger VTX at 1200mW either pad is fine.

I'm going with the 9V, lower amperage, and possibly cleaner since there are less "users" on the FC's 5V supply. Wooo, I'm an expert

I have the board, VTX, and Rx all wired up and working correctly now. The Flywoo Goku F745 EVO was a bit of a problem child. It came with BF 4.3.1 and I was unable to connect the VTX. Out of the box there were red lines of type in the dump files regarding the VTX:
set vcd_video_system =
###ERROR IN dump: CORRUPTED CONFIG: vcd_video_system = 3###
No CLI commands or Presets could fix that so I flashed BF 4.4.3 and proceeded with that. Connecting the Radiomaster RP3 ELRS Rx was easy but I had a head scratcher or two getting the BF OSD to display, and display correctly, in the Walksnail goggles. But loading the DJI VTX Preset got it then cycling some commands on the OSD page got the correct HD layout in my goggles. Yay.

Next up is mounting the board and connecting the motors. Any recommendation for motor settings would be appreciated. Components are:
Flywoo GOKU GN F745 EVO HD 2-6S 20x20 AIO Flight Controller w/ 40A 32Bit 4in1 ESC
BROTHERHOBBY VY 1504.5 3950KV MOTOR
Any recommendations for a Preset BF Tune for this 250g 3.5? That might have motor settings... Or use BF default?

Hi Husafreak,

Just my 2 cents worth.

Very first thing, be sure to back up the default Betaflight settings. At the
very least a DUMP ALL and a DIFF ALL. 

Consider taking a few test flights with the default tune, before you change
anything. Each build is a bit different, so until you know how it flies with
the default settings, what characteristic would you be trying to "fix" or
"tune". Maybe, fly it first, see how it flies. 

Here is a scenario that I keep seeing. Someone builds a quad, maybe 
their first. Next, they fiddle with all sorts of tuning, PID settings, ESC
settings, and who knows what else. Ok, fine. Then they take the quad
out for a flight and is flies horrible if at all. Now, they ask, what is wrong;
how do I fix this or that. 

My concept is to assemble the craft, do a very basic Betaflight configuration
which is mostly setting up the ARM and Fly Mode switches and maybe a bit
of OSD adjustment leaving all of the tune just as it came. Next, I fly the
craft. First, a simple take off and hover at about 4 feet and very slight stick
movements just to confirm that the controls seem to work. Next, I move 
outside for a few LOS test flights to get an idea how the quad responds 
to stick movement. At this point, I know that I have something that will
at least fly. Except for one build, my quads are running on the default
(stock) tune and PID settings. Since they fly just fine, I see no reason to
mess with the tune: If it ain't broke, Then DON'T fix it. 

I have a 4" build, my Katana-LR4, running the same BH motors and 
pretty much the same specs and an all stock, default, tune and she flies 
just fine. My suggestion would be to fly it before you start changing things.

Just me. 

Later, iFly  

That sounds like good advice. I do believe that the Betaflight developers strive to provide a good default tune as a starting point. And in the past my attempts to tune my quads have been pretty poor. I mean changing rates, adding expo, that is easy and quick, but with PID's and Filters I am as likely to make things worse as I am better. I do like the Betaflight Preset Tunes though. I figure they are made by better pilots that know what they are doing, ha ha!
As for the DUMP and DIFF ALL that is what I always do and I was pretty surprise to see "###ERROR IN dump..." right off the bat. Who knows, maybe I got a board someone returned?

I do need to make sure my motor tab settings are OK. After the flash I had to enter settings. I just selected DSHOT600 because it is familiar. I'll go back and look at the dump with the "ERROR" and see if I can read what was on there before.

From DUMP:

set dshot_idle_value = 550
set dshot_burst = OFF
set dshot_bidir = OFF
set dshot_bitbang = AUTO
set dshot_bitbang_timer = AUTO
set use_unsynced_pwm = OFF
set motor_pwm_protocol = DSHOT600
set motor_pwm_rate = 480
set motor_pwm_inversion = OFF
set motor_poles = 14

The Brother Hobby motors are 12N14P so it looks like I'll be fine.

I got a 30 second test hop in today It flies. I’ll do pics and go over the build later. One crazy thing I learned today. I have never bothered to tell my quads which direction the props are turning on the Betaflight motors page. Now I gotta go back and check all my quads. With this one it won’t fly right if the props are reversed and you forget to check that box in BF. I learned something today

The frame uses 3 standoffs, I chose 25mm and I'm glad I did. The front two use 2mm bolts and hold the TPU printed 14mm camera mount. The rear one is a larger diameter using 3mm bolts. The rear TPU antenna mount has a slot for the CF top plate so it will not swivel.