what is the maximum range to connect 2 NRF51822 devices with Gazell

[Tim]

Hello,

I was looking into Gazell and read that Gazell only allows pairing when Host and Device are in close proximity to each other. This range is about 30 centimeters. I was wondering if this range could be extended? and if this is possible what will be the range it could reach?

Thanks in advance,

Tim

[Jørgen Kvalvaag]

This is a security feature implemented in the gazell pairing library, to prevent bonding to any "wrong"/malicious device. This library is delivered as source code in the SDK, so it is possible to change this behavior.

Basically the gazell library transmits the pairing request using low (-16dBm) tx power, so only devices in close proximity will receive it.

To be able to do pairing using normal tx power one only needs to change one line in the file nrf_gzp_config.h(line 53):

/**
Reduced TX power for use during close proximity pairing.
*/
#define GZP_POWER NRF_GZLL_TX_POWER_N16_DBM

change to:

#define GZP_POWER NRF_GZLL_TX_POWER_0_DBM

[Tim]

Hello, Thank you for the quick response :).

[Sigurd]

The close proximity pairing feature in Gazell uses the RSSI measurement to detect if a device is in pairing range.

On the host side, the RSSI is compared against a threshold to decide if the device is in range, and is defined as

#define GZP_HOST_RX_POWER_THRESHOLD -64 ///< RSSI threshold for when signal strength in RX packet power is high enough.

If you want to extend the pairing range, you can adjust this threshold to fit your requirements.