Design a FC for INAV

[digitalentity]

I think it's time to think about designing a FC specifically for INAV.

Features I want to have on this FC:

1. Future-proof design with an F4 (or even F7) CPU
2. 8 outputs supporting 8/0, 6/2, 2/6 motor/servo configurations
3. Onboard baro (MS5607 or BMP280)
4. Optional onboard NRF24 receiver (placeholder for a tiny daughter PCB)
5. External I2C connector (compass)
6. External SPI connector (opflow)
7. SD-card logging
8. Hybrid 4-pin connector to PWM/SBUS receiver (3.3V + 5V both available), same pin used for PPM/SerialRX
9. USB VCP
10. At least 3 extra UARTs for GPS, MSP, Telemetry
11. 5V-level LEDSTRIP connector
12. Analog inputs for RSSI, VBAT, CURR and an extra for optical rangefinder
13. Sonar connector

What do you think?

[skaman82]

13 Sonar Pads

[Linjieqiang]

Wonderful!I have always been concerned about this project.I am designing a FC board now and ready to flash inav F4 firmware,use STM32F4RGT6.I suggest why not use Can Bus Hub like Dji to connect sonar,opflow,gps,osd or even more sensors and devices?It will save hardware resources.

[DzikuVx]

What about factor? Probably keeping 30-something (30.5mm hole spacing) would be impossible. I'm fine about that, Pixhawk size would be totally fine in my case. I would even prefer that.

It would be also very nice to have SoftSerial not conflicting with RSSI and ADC

[digitalentity]

@skaman82
Done!

@Linjieqiang
I'm thinking about being able to connect a sensor hub via serial port - this way sensor hub will be usable even with older FCs without CAN. I don't want this design to be bound to one hardware only.

@DzikuVx
I'm going to keep 30.5mm hole spacing but the overall form factor is going to be larger (longer board). USB on the side, connectors on front and rear edges.
I'm not going to make SoftSerial available on this board - F4 CPUs have enough hardware UARTs.

I'll design the board in such a way that it would be possible to use all (or almost all) features at once without conflict.

[skaman82]

1+ for 30.5mm hole spacing

[DzikuVx]

I would be very happy with 5 Hardware Uarts

[digitalentity]

@DzikuVx this might be impossible. I'm going to use UART2 RX for PPM/SERIALRX input so it's going to be UARTS 1,3,4,5

[DzikuVx]

I know I am an special case here. I have OSD via MSP, another msp for telemetry, GPS, FrSky S.Port and Blackbox. All 5 possible Uarts taken on my Sprf3.
Probably will switch osd to ltm and share it with telemetry via some Small arduino to free one uart

[oleost]

Just a question.

Hardware UARTS are fine, yes. But Softserial has proved very usefull in many cases.

With an F4 cpu compared to an F3 CPU could we overcome some of the limitations?
Or with the F7 cpu?

Not a hardware developer, nor a software. Just thinking with a more powerfull CPU maybe softserial could run at 100k baudrates?

[bk79]

I would use mpu9250 to have compass with no extra wire and an integrated
bec so to avoid having a different board and all the io pin out avaiable
Il 15/giu/2016 11:52, "Konstantin Sharlaimov" notifications@github.com ha
scritto:

I think it's time to think about designing a FC specifically for INAV.

Features I want to have on this FC:

1. Future-proof design with an F4 (or even F7) CPU
2. 8 outputs supporting 8/0, 6/2, 2/6 motor/servo configurations
3. Onboard baro (MS5607 or BMP280)
4. Optional onboard NRF24 receiver (placeholder for a tiny daughter
   PCB)
5. External I2C connector (compass)
6. External SPI connector (opflow)
7. SD-card logging
8. Hybrid 4-pin connector to PWM/SBUS receiver (3.3V + 5V both
   available), same pin used for PPM/SerialRX
9. USB VCP
10. At least 3 extra UARTs for GPS, MSP, Telemetry
11. 5V-level LEDSTRIP connector
12. Analog inputs for RSSI, VBAT, CURR and an extra for optical
    rangefinder

What do you think?

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[skaman82]

@bk79 External compass mounted far away from the wiring is always better then a internal one.

[DzikuVx]

And this is why I like the idea of no magnetometer on this board

[bk79]

As long as it is far from ac power source (escs) it's ok and unless you
have a 250 size which is intended normally for racing i can assure it
makes really little difference to have it inside or outside the fc shell if
you like i can attach the reading coming from a sparky connected to an hexa
320 and the reading coming from a cc3d connected to an 400size with ext
compass of course in hoovering conditon for both that means low currents
radiating
Il 15/giu/2016 13:07, "Paweł Spychalski" notifications@github.com ha
scritto:

And this is why I like the idea of no magnetometer on this board

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