Bug or doc issue?

Hi there,

I’m testing the access to the DWM1001 through BLE connection. So I’m using the DWM1001 Bluetooth API doc as the guide to know how to access the several characteristics provided by the module.

I’ve got an issue when accessing the Device Info characteristic (UUID 1e63b1eb-d4ed-444e-af54-c1e965192501). According to the doc (pag 8), it should return 29 bytes with layout…

Node ID (8 bytes), HW version (4 bytes),
FW1 version (4 bytes), FW2 version (4
bytes), FW1 checksum (4 bytes), FW2
checksum (4 bytes), RDonly Operation
flags (1 byte)

However, I’m getting only 22 bytes and the layout seems to fulfill the expected one at least until the FW2 version field. There are 2 final bytes that do not match to anything expected and I do not know how to use them. I have checked this using a third-party BLE scan application (from Nordic) and the data I am receiving and showing in my device are the data actually being sent by the DWM1001 (so no software coding error in my side).

So… is it a bug in the firmware API or a documentation failure ?


Hi YoHidden,

What is the nordic software you’re using by curiosity ?

I’ll take a look at the BLE api and will come back to you.


Hi Yves,

The Nordic app is for the iPhone and it is called nRF Connect.


Hi YoHidden,

I just checked with nRF connect on my Android phone, and got 29 bytes back from the uuid you mentioned. The values seem correct.


Hi Weibo, thanks for your answer.

I do not understand how can this be. The only thing I can think of is that from these data you’ve sent, it seems that FW version bytes are (FW1) 00-00-03-01 and (FW2) 01-01-00-03, which are definitely different to the ones in my devices.

I don’t have the device with me right now so I can not check it in this very moment, but I will this afternoon and will come back to you to send an image with the data being received.


I just flashed with an old release, and got the below result…

so, this time i got 29+16 bytes… first 29 bytes are good, and then followed by 16 bytes 0x00



Ok, I’ll send you my images in a couple of hours.

Meanwhile, what is the latest version of the firmware and where can I get it?


Oops… I must apologize for this. It has been totally my fault.

My nRF Connect application is showing also the 29 bytes being sent by the DWM1001, so the problem is in my side. I can’t believe that I miscounted the bytes on screen so I thought that only 22 bytes were being sent. I sincerely apologize for wasting your time. The 22 bytes are only the first chunk of data being sent for a characteristic with number of bytes longer than 22… :cold_sweat::zipper_mouth_face:

And about the firmware version, mine is (data received 01 01 05 01)… is it the last version?

Thanks (…and sorry again).

Good to hear that there’s no problemo :smile:
The latest released version should be

Hey there,
I encountered a similar problem: I’d like to send distance data from the tag to my mobile via BLE. The documentation in the API Guide tells me that I should expect 29 bytes coming from the tag after each measurement. But for some reason I always only receive 20 bytes. When I set the location data mode to “Position only”, it works an I receive 14 bytes. But when I set location data mode to “Distance only” or “Position and Distance” I always only receive 20 bytes.
It looks like 20 byes is the limit. How can I extend that limit? @YoHidden how did you receive all your data in total?

I found the solution for my problem. It is explained here: