Hello everyone,

I was looking to add a Barometer (BMP180) and a GPS module (Ublox) on my Mamba F405 stack to give it some additional features such as altitude hold and performing way-point missions.

After going through the layout of my FC and pinouts of the sensors I found out that barometer and GPS both need the SCL and SDA pins but my board has only one set of those pads.

What do I do? Are there other ports that can be used? Or should I consider buying an FC board with an in-built baro sensor?

Thanks.

Hi,
You can connect multiple devices to the SCL and SDA pads. I have the same configuration and everything is detected correctly. I connected the GPS to UART6, the barometer and compass (from the GPS) to SCL, SDA.

Since I went through the gps/compass hassle recently, here are my 2 cents.
GPS does not need scl/sda. Just regular uart.
But compass does need scl/sda. For pos hold/way point missions/rth in inav i believe you would need compass.

But that leave the question of do you have 2 scl/sda ports?

(09-Dec-2019, 03:08 PM)sim_tcr Wrote: But that leave the question of do you have 2 scl/sda ports?

like @ssombra wrote:
SCL/SDA are just connected parallel. Every sensor has a built in hardware id and they share the bus. No need for 2, they work differently then UART

(09-Dec-2019, 03:08 PM)sim_tcr Wrote: Since I went through the gps/compass hassle recently, here are my 2 cents.
GPS does not need scl/sda. Just regular uart.
But compass does need scl/sda. For pos hold/way point missions/rth in inav i believe you would need compass.

But that leave the question of do you have 2 scl/sda ports?

Thanks for your reply.
This board has only one scl/sda port.

(09-Dec-2019, 03:04 PM)ssombra Wrote: Hi,
You can connect multiple devices to the SCL and SDA pads. I have the same configuration and everything is detected correctly. I connected the GPS to UART6, the barometer and compass (from the GPS) to SCL, SDA.

Thank you for your help!!
I will try that. Would BMP280 and Ublox Neo M8 be a good choice or what do you recommend?

(11-Dec-2019, 02:23 AM)abhivaya Wrote: Thank you for your help!!
I will try that. Would BMP280 and Ublox Neo M8 be a good choice or what do you recommend?

Bmp280 is standard one comes on all FC’s with built in Baro.
GPS, I have Bn-880 which is good. But if you have budget go for the matek gps. Many people rated it high.

(11-Dec-2019, 02:44 AM)sim_tcr Wrote: Bmp280 is standard one comes on all FC’s with built in Baro.
GPS, I have Bn-880 which is good. But if you have budget go for the matek gps. Many people rated it high.

Thanks!!
As a total noob (and a student) I wouldn't want to expand my budget. For my learning curve I think Bn880 or Ublox are a better choice.

bn-880 is pretty huge, i own a used one, but it wasnt in use allready. i had tries with bn-220 and bn-180, both are inexpensive and did work well - but i havent enough experience..

I’m using Crossfire RX on UART 6. I need a UART (RX&TX) available for the GPS. Where can I connect it?
Do I need to remap resources in Betaflight? If that’s the case, I’m thinking about disconnecting TX3 (used for SmartAudio), totally freeing UART3 for the GPS and then remmaping SmartAudio to maybe... the LED control tab? (I don’t use LEDs)
I also thought about using 2 of the LED pads as Softserial RX & TX... but I’m not sure how to identify which one is what on the FC...
Would any of these options work?
Any suggestions? Thank you!!

PS
Version 1 of this same FC has TX1 & RX1 on the board, but they changed it in MK2 in order to include LEDs

(13-Dec-2019, 06:45 AM)Anders Wrote: I’m using Crossfire RX on UART 6. I need 2 available UARTS for the GPS. Where can I connect it?
Do I need to remap resources in Betaflight? If that’s the case, I’m thinking about disconnecting TX3 (used for SmartAudio), totally freeing UART3 for the GPS and then remmaping SmartAudio to maybe... the LED control tab? (I don’t use LEDs)
I also thought about using 2 of the LED pads as Softserial RX & TX... but I’m not sure how to identify which one is what on the FC...
Would any of these options work?
Any suggestions? Thank you!!

PS
Version 1 of this same FC has TX1 & RX1 on the board, but they changed it in MK2 in order to include LEDs

Hi, I am not sure which GPS you are using, but usually the GPS only needs one UART. If the GPS includes also a compass (magnetometer) then you need to connect it to the SDA SCL pads, not to a UART.

thanks for your reply, I guess I didn’t explained myself correctly.
All GPS modules I have used need RX and TX.
There’s only UART3 (RX3&TX3), and UART6 (RX6&TX6) available in this board. I’m using Crossfire RX on UART6. I can’t use UART3 for GPS, because as I mentioned, TX3 is in use with SmartAudio.
So I’m thinking: 1. either I disconnect SmartAudio on TX3 in order to free UART3 (TX&RX) and then route SmartAudio to another tab, or, 2. I leave SmartAudio alone and create a Softserial UART (TX&RX) by remapping resources in Betaflight. There is no UART1 on the board as there was on previous version of this FC.

If I choose 1., where should I remap SmartAudio?
If I choose 2., which tabs would work to create a SoftSerial UART? I thought about using some of the LED tabs, but I’m not sure how to identify which one is which on the resources map on Betaflight.

(13-Dec-2019, 06:18 PM)Anders Wrote: All GPS modules I have used need RX and TX.
There’s only UART3 (RX3&TX3), and UART6 (RX6&TX6) available in this board. I’m using Crossfire RX on UART6. I can’t use UART3 for GPS, because as I mentioned, TX3 is in use with SmartAudio.
So I’m thinking: 1. either I disconnect SmartAudio on TX3 in order to free UART3 (TX&RX) and then route SmartAudio to another tab, or, 2. I leave SmartAudio alone and create a Softserial UART (TX&RX) by remapping resources in Betaflight. There is no UART1 on the board as there was on previous version of this FC.

If I choose 1., where should I remap SmartAudio?
If I choose 2., which tabs would work to create a SoftSerial UART? I thought about using some of the LED tabs, but I’m not sure how to identify which one is which on the resources map on Betaflight.

GPS really needs to run on a hardware UART to get the most out of it because it needs a faster baud rate than SoftSerial can offer. I would therefore remap SmartAudio to the PPM pad leaving UART3 for GPS. SmartAudio runs just fine on the lower baud rate offered by SoftSerial. To remap / reconfigure Betaflight on the Mamba F405 FC (which uses the FURYF4OSD Betaflight target), run the following commands in the CLI. These will remap SmartAudio to the PPM pad, configure SmartAudio to use SOFTSERIAL1, and configure GPS to run on UART3.

Great! Thank you for taking the time to do this.
I’ll try it tonight!!
THANKS!!!!!!

- it worked perfectly. I really appreciate your help.
All the best!

(13-Dec-2019, 06:45 PM)SnowLeopardFPV Wrote: GPS really needs to run on a hardware UART to get the most out of it because it needs a faster baud rate than SoftSerial can offer. I would therefore remap SmartAudio to the PPM pad leaving UART3 for GPS. SmartAudio runs just fine on the lower baud rate offered by SoftSerial. To remap / reconfigure Betaflight on the Mamba F405 FC (which uses the FURYF4OSD Betaflight target), run the following commands in the CLI. These will remap SmartAudio to the PPM pad, configure SmartAudio to use SOFTSERIAL1, and configure GPS to run on UART3.

Code:

resource PPM 1 NONE
resource SERIAL_TX 11 C09
feature SOFTSERIAL
serial 2 2 115200 57600 0 115200
serial 30 2048 115200 57600 0 115200
save

Bro, if i use UART3 for Crossfire Nano Rx, and UART6 for DJI Air Unit, is there anyway to find another UART to connect a GPS? Really appreciate your help