HERE2 Serial protocol


The Here2 works fine when configured as serial gps in Ardupilot.
I tried to connect it to U-Center via serial with no success.
When looking at the packet received it is not the ASCII NMEA usually ouput by U-Blox and other GPS’s.

I didn’t find any documentation about the serial protocol used for the Here2.

Could anyone tell me about the protocol used by the Here2 firmware (STM32f3) to communicate on the serial port ?


Connecting Here2 to u-center should be similar to Here+

But you need to try different baud rate until you found the correct value. Sometimes the ublox chip has different connection baud rate for some reason.

Hi @Alvin thanks for the answer,

I tried all the baudrates as well as autobaud in the U-Center software with no success.
My FTDI converters works fine, the wiring is ok, and I get binary packets instead of ASCII NMEA.
U-Center does not detect anything

I still don’t understand how the U-Blox module is connected and what the STM32f3 is used for when in Serial mode.
Does Here2 act as a sort of pass-thru between U-Center and the U-Blox module inside Here2 ?
Or is the U-Blox module connected directly on the serial lines that goes out of the Here2 ?


You need a USB to serial converter like CH340. The Here2 does not send RS232 protocol.

The STM32 on Here2 is a pass-through to the u-blox chip. However, they are also on the i2c bus. You can also directly connect to the onboard sensors if you want.

Thanks for the answer,

I have no CH340 but the serial adapters I use are similar USB to 5V TTL serial.

What is bothering me is that this GPS works fine via serial in Ardupilot yet I cannot connect it in U-Center.
Does Ardupilot uses a specific driver, although the port is simply configured as GPS, 38400 bauds ?


The ardupilot auto detects the baud rate to connect u-blox chip.
But for manual connection in u-center, you have to try every baud rates one-by-one.
By default it should be 9600 or 115200, but sometimes it would be different for some reason

It sends and receives ubx which is the uBlox binary