Maximize range on nRF52840 pdk

[daguro]

How do I maximize range for BT5?

I have two nRF52840 pdk units and I have loaded the ble_app_att_mtu_throughput app and tried it out. I have been seeing around 70 meters range before the link drops out. What can I do to get maximum range?

[Ole Bauck]

Hi,

You can change the PHY to CODED. This will set the on-air bitrate to 125kbps which is a new feature of nRF52840 called long range Bluetooth, and will give you about 7dBm more sensitivity compared to 1Mbps, see here. You can do this if you use the example from SDK 13.0.0-1.alpha and SoftDevice S140 5.0.0-1.alpha (SoftDevice for nRF52840). There is an option called "Select preferred PHY".

You can set the tx power higher. The default in the example is 4dBm (supported by both nRF52832 and nRF52840). nRF52840 has an internal PA capable of tx power up to 8dBm. This is not an option to set while you are running the example, so you have to go into the code and change this. Look for the tx_power_set() function and change it to:

void tx_power_set(void)
{
    uint32_t err_code;
    err_code = sd_ble_gap_tx_power_set(8);
    APP_ERROR_CHECK(err_code);
}

You should also set the connection interval to the minimum (7.5ms). This will lower the time between each resent packet if you start loosing packets.

The features of nRF52840 is summarized here.

[daguro]

That worked.

Thanks for your help.

[Scott]

What range did you end up getting after changing these? And was this in open air, line-of-sight?

[daguro]

I paced off 110 meters and had no problems. I didn't repeat the test at 4 dbm. I'm pretty sure that I would have had no problems.

[Scott]

Good to know, thanks!