What should be the "NRF_RADIO" configurations to establish in maximum distance connection?

[purgoufr]

I have one central(SDK 10.0 S130) and one peripheral(SDK 8.0 S110) device. Normally central device can connect peripheral device it's ok but the peripheral device will stay in metal case. I did some tests and I saw that when I put it in the metal case, the distance I needed to connect was too short. What can I do to resolve this problem? The solutions coming to mind are Antenna and Radio Configurations ( NRF_RADIO->TXPOWER, MODE, FREQUENCY etc.). Do you have any suggestion about that?

[Jørn]

Hello Purgoufr

A metal case will function as a Faraday cage and cause great attenuation to the electromagnetic signal. The best solution would of course be to move the antenna to the outside of the case. If this is not possible then openings in the metal case (air holes etc.) can allow the signal to bleed through. Do note the number of openings, the distance between openings, the size of the openings and the thickness of the metal will all affect the attenuation of the electromagnetic signal.

Another thing to consider is that the metal casing will affect the antenna itself, and can change its impedance and resonance frequency. So an antenna that is perfectly matched outside the metal casing can be mismatched inside the metal casing.

As for radio settings the output power should be set to its maximum (+4dBm). If you are using a proprietary protocol you can reduce the bit-rate down to 250kb/s to allow the receiver more time to interpret the incoming symbols, but if you're using BLE you're stuck with 1Mb/s.

Beyond this there are not that many options for the nRF51822. Alternatively you could try using the nRF52840, as its long range features (increased output power and forward error correction) could make quite an impact.

Best regards

Jørn Frøysa

[purgoufr]

Hi Frøysa,

Thank you very much for the information you provide. The peripheral device can be connected in the metal case, from the phone's bluetooth, the nrf connect application, and the dongle, but I can not connect from the central device. If metal case cause function as a Faraday cage and cause great attenuation to the electromagnetic signal, So how did I get connected with phone's bluetooth , dongle or nrf connect app?

[Jørn]

The quality of the faraday cage will depend on the material used and if there are any holes in it. It may be that your metal casing is letting enough of the signal out for you to connect to it. If you are able to connect with other devices I suspect it has something to do with the location and set up of your central device.

[purgoufr]

I thought The Bluetooth antenna of the phone is more powerful and the phone's stack is more efficient. That's why I am researching how to improve. Additionally, when I try without metal case central device working smooth. So the problem is antenna or radio configurations . NOTE; I tried that in main.c; //Radio Config NRF_RADIO->TXPOWER = (RADIO_TXPOWER_TXPOWER_Pos4dBm << RADIO_TXPOWER_TXPOWER_Pos); NRF_RADIO->MODE = (RADIO_MODE_MODE_Ble_1Mbit << RADIO_MODE_MODE_Pos); NRF_RADIO->FREQUENCY = 79UL; // Frequency bin 7, 2407MHz

But there has not been any change.

[Jørn]

It is difficult to say precisely what is allowing your phone to connect and not your central without proper insight into the physical set up of your system. If you are using the SoftDevice you will not be able to configure the radio directly like that as the SoftDevice will take control of the radio peripheral. Please see section 11 and table 22 of the S110 documentation. You will need to use the SoftDevice API to change the radio settings.