Set the transmit power on NRF51822

RE: Set the transmit power on NRF51822

Simonr — Thu, 17 Oct 2019 10:42:42 GMT

Thank you for your update, I was not aware of this, sorry about that. Glad you were able to figure it out!

Best regards,

Simon

RE: Set the transmit power on NRF51822

Rashmi — Thu, 17 Oct 2019 09:27:28 GMT

Hi Simon

We have contacted the LAIRD to check if there is any hardware issue with the module. They suggested us to set PO.20 LOW(0) to get 4dBm normal Tx power. Set PO.20 HIGH(VCC) to get Tx whisper mode power(-30dBm to -55 dBm).

In our application we have set the pin PO.20 to low and now we are getting the range approximate 12 meters inside office environment. Seems like they have some hardware configuration to allow the module to transmit at higher power when PO.20 made low.

Thanks for your support.

Thanks,

Rashmi

RE: Set the transmit power on NRF51822

Simonr — Thu, 17 Oct 2019 06:40:21 GMT

Hi Rashmi

That seems very strange. Do you use the antenna on the module itself or have you built a custom board around it? Is the device in some sort of casing or similar? This does not seem like a problem with the TX power to me, but rather a hardware issue. If you want, I can set this case to private mode and take a look at your schematics and PCB layout (if this is a custom board, that is).

Best regards,

Simon

RE: Set the transmit power on NRF51822

Rashmi — Wed, 16 Oct 2019 12:20:15 GMT

Hi Simon

We are able to get the maximum of -100dBm for all the Tx power levels at the distance of 30cm. If we increase the distance we are not able to detect the Bluetooth device.

Thanks,

Rashmi

RE: Set the transmit power on NRF51822

Simonr — Wed, 16 Oct 2019 08:07:30 GMT

Hi Rashmi

As per the BL600-SA datasheet, the typical receive sensitivity is at -91dBm (which could easily be -95 in an office environment). At what range does the chip stop advertising altogether with the different TX powers, I don't think you'll be able to see any differences up close with the antenna that is on the BL-600.

Best regards,

Simon

RE: Set the transmit power on NRF51822

Rashmi — Tue, 15 Oct 2019 12:37:32 GMT

Hi Simonr,

We are getting the RSSI value of -95dBm at any of the Tx power levels. If we place central and peripheral very closer i.e less than 2cm, we are able to get the RSSI value of -76dBm.

Thanks,

Rashmi

RE: Set the transmit power on NRF51822

Simonr — Tue, 15 Oct 2019 07:18:28 GMT

Hi Rashmi

Okay, then it might be that the signal strength won't get any higher than it already is at the close range. How much is the RSSI value at any of the TX power levels? You can try moving the peripheral further and further away from the central, as you should see the RSSI drop faster (at a lower range) at a lower TX power.

Best regards,

Simon

RE: Set the transmit power on NRF51822

Rashmi — Mon, 14 Oct 2019 09:12:30 GMT

Hi Simonr

We have tested the ble_app_proximity example in SDK 12.3. We are not finding any difference in the RSSI value(with -8 and 4dBm Tx power level). We have also tested the example code with two different modules, but the results are same.

Thanks,

Rashmi

RE: Set the transmit power on NRF51822

Simonr — Mon, 14 Oct 2019 06:23:24 GMT

Hi Rashmi

I also tested the example in SDK10 with S110, and I am able to see an increase in RSSI when testing as I did with SDK12.3 and SoftDevice S110. Approximately the same difference between 4 and -8 dBm where I can see the signal going from ~50dB to ~40dB. Are you sure you're changing the "#define TX_POWER_LEVEL (4)" in your main.c function? And are you sure that you build the project before flashing it to the chip?

Note: I used the Keil µvision 5 IDE to compile and flash this program, so there might be some issues with IAR for the SDK 10 (I'm not sure about this though, as the SDK is rather old, and I'm not too familiar with IAR).

Best regards,

Simon

RE: Set the transmit power on NRF51822

Rashmi — Fri, 11 Oct 2019 13:32:50 GMT

Hi Simonr,

I didn't test example with SDK 12.3. Will do it on Monday. If the issue with hardware, then in the other board it should have worked as the module was powered for first time and also flashed for the first time.

The RSSI is exact same and there is no much difference.

nRF5x_MDK_8_2_0_IAR.msi was in the SDK10 folder when we downloaded from the Nordic website. We will try to install the latest version of MDK file and let you know the result after testing.

Thanks,

Rashmi.

RE: Set the transmit power on NRF51822

Simonr — Fri, 11 Oct 2019 13:21:10 GMT

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

RE: Set the transmit power on NRF51822

Rashmi — Fri, 11 Oct 2019 12:54:35 GMT

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

RE: Set the transmit power on NRF51822

Simonr — Wed, 09 Oct 2019 12:26:12 GMT

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

RE: Set the transmit power on NRF51822

Rashmi — Wed, 09 Oct 2019 10:41:43 GMT

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

RE: Set the transmit power on NRF51822

Simonr — Wed, 09 Oct 2019 09:20:24 GMT

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