Set the transmit power on NRF51822

[Rashmi]

Hi

We are using BL600-SA in our project. I need to configure NRF51822 transmit power so that it is discoverable at particular distance.

I am using softdevice S110 and I tried to set the Tx power using sd_ble_gap_tx_power_set() function, but I did not finding any difference 

in the RSSI value. The API is returning NRF_SUCCESS. I have also tested with softdevice S130, but that is also not working us.

Can anyone please suggest me the way to configure the transmit power level?

Regards,

Rashmi

[Simonr]

Hi Rashmi

What value are you setting the TX power to and from what value is it set? Depending on the environment you're testing in, the RSSI might not change much from one TX power setting to the next. Please describe your testing environment. What range are the devices from one another? What interference sources might be present? Are the devices in line of sight of one another? I think you're setting the TX power correctly, but you're just not seeing the change in RSSI for some reason. Try setting the TX power to a low number to see if the RSSI decreases.

You can check out this case to make sure you're doing it correctly.

Best regards,

Simon

[Rashmi]

Hi Simon,

Thanks for quick response.

Our device will be communicating with Phone and works as peripheral. Initially the default value was set, but after testing we have set the TX power to 4. We have done testing by setting other TX power values but the results are same. We are testing the device inside the office and the both peripheral and central are in line of site. The distance between phone and our device is approx 40cm. For testing purpose we are using Light Blue App. 

We have even tested the same code in another board and the result are same.

Thanks,

Rashmi

[Simonr]

Hi Rashmi

I just tested the ble_app_proximity example in SDK v.12.3 on one of my nRF51 DKs and got a drop in ~10dBm when I changed the TX value from 4 to -8. This is in an office environment with quite a few interference sources and a lot of BLE activity, but the devices were in line of sight of one another and about 30cm apart. I used the nRFConnect app on my phone for testing. Below you can see a screenshot of the RSSI graph (dark blue being the proximity device).

Could you try this example as well to confirm whether you're able to see a difference or not? You can change the TX_POWER_LEVEL value to change the TX power here. It could be that the TX power is set to a specific value somewhere else in your application that overwrites your settings.

Best regards,

Simon

[Rashmi]

Hi Simon,

The custom project is built using SDK v.10 and SD110. We tried to increase the TX power level using sd_ble_gap_tx_power_set(), but still no improvement in the RSSI. We would also like to know whether we need to install nRF5x_MDK_8_2_0_IAR.msi and then provide the path in IAR.

As we are using the Module from Laird we are not suspecting any issue with respect to antenna tuning or the antenna used. The same code we tested in another board and the result are same.

As per Nordic Semiconductor if the power level is set to '0' we should get a rage of 10-15 meters (We know the range depends on the environment).

We could not try an example project with SDKv.12.3 as it wont support SD110.

We would like to know what other setting may affect the range?

Thanks,

Rashmi

[Simonr]

Hi

Are you able to test the example in SDK12.3 using SoftDevice S130? You can flash the device either using Keil µvision, IAR, or the nRFConnect for Desktop programmer app. If you can test with that SDK we'll be sure whether the issue is the hardware or software.

I'm not an expert in IAR, but I recommend you do download and install the latest MDK version. 

Btw, what is the current RSSI you see when using the SDK 10 and S110 application, and is it the exact same (within +-2dBm) or does it increase/decrease at all?

Best regards,

Simon