Error 133 (0x85): GATT ERROR

[PabloGC]

Hello everyone,

I know this issue is quite recurrent but I've gone crazy reading so many different issues with android version, Connection intervals, etc. Would like to know if someone can help me looking for an answer that fits the description of my problem or just forward me into a direction to solve the issue.

So, I've tried my firmware on the nRF SDK and everything works perfectly (Samsung note 2 connects fine and also a Xiaomi phone) but whenever I try to connect to my custom board, the phones cannot connect to it and I get this nRF Connect log:

    nRF Connect, 2017-11-27
Malapascua (D9:1C:BF:F2:0E:03)
V	16:20:44.774	Connecting to D9:1C:BF:F2:0E:03...
D	16:20:44.774	gatt = device.connectGatt(autoConnect = false, TRANSPORT_LE) (hidden)
D	16:21:05.631	[Callback] Connection state changed with status: 133 and new state: DISCONNECTED (0)
E	16:21:05.631	Error 133 (0x85): GATT ERROR
I	16:21:05.631	Disconnected

The only noticeable difference is the RSSI: nRF SDK moves between -30 up to -43 dBm while my custom board is between -70 up to -80 (really bad connectivity).

Here is my schematic:

And here is also my layout (units in mm):

• Purple is stiffener plane
• Blue is Bottom Layer
• Red is Top Layer

The antenna track is 0.762 mm width with 1 oz thickness.

Thank you,

Pablo G

[PabloGC]

Thank you very much Jorn, I will take more care when redoing the layout. I just wanted to make sure the error 133 was happening because of the bad connectivity and not something I was missing in the schematic. As I said, the program I'm uploading works absolutely fine with the nRF SDK so it should also work with my custom board, right? (I just want to discard any firmware incompatibilities)

[Jørn]

The fact that it is working perfectly on your devkit does indicate that your firmware is OK, especially if the chip on your devkit and custom board are the same revision versions. You registered an RSSI of -70 to -80 dBm on your custom board. Considering the nRF51 has a sensitivity of -93 that only gives you a headroom of 23 to 13 dB. In an indoor or urban environment that isn't all that much.

You could try to use a sniffer and see what exactly is exchanged between the two devics before the disconnect. This would give you a further indication as to whether the disconnect is a firmware error or not.

[PabloGC]

Do you know any phone app that I can use as a sniffer? I already tryied Wireshark in my computer but I was having so many problems with the set up that I drop it...

[Jørn]

Unfortunately I don't know of a mobile app. The sniffer software is a bit old, so it can be a bit troublesome to get going. It requires version 1.10 of wireshark, later versions won't work. The sniffer devkit must be a nRF51 (f.ex. the pca10028) and the on board J-link debugger firmware should be downgraded to version 5.1, you can find a link to version 5.10n in this blogpost. After you've installed the j-link software you can open the J-link configurator from the correct folder in the start menu (for windows) and replace the firmware of the kit.