STEVAL-MKBOXPRO BLUENRG-LP Transmit Power cannot be changed ... in practice

[dufaza]

Hi,

i experimented the following configuration STEVAL-MKBOXPRO with BLEMLC code available within FP-SNS-STBOX1 package. For my specific application, i want to increase the BLE transmit power of the BlueNRG-LP chip of the MKBOXPRO. So i modified the code with the aci_hal_set_tx_power_level(1,31) +8dBm (since default value was  aci_hal_set_tx_power_level(1,4) -16dBm). Everything is fine with compilation with Cube IDE.

But in practice with the app ST BLE Sensor v5.2.6, the real connection distance still remains about 25m, with a disconnect when RSSI is about -92dBm. These values are correct but what is not correct is that any tries to change aci_hal_set_tx_power_level with different "theoretical" power levels (from -54dBm to +8dBm) do not change anything in practice. It looks like aci_hal_set_tx_power_level has no effect on "real" transmitted poser.

Any help will be welcomed to this topic.

Thanks reading et thanks in advance or your help. Christian

[dufaza]

I solved this problem … but i don’t know how to close this topic !

[Andrew Neil]

i don’t know how to close this topic

Tell us how you solved the problem, and then mark that post as the solution.

[Andrew Neil]

​@dufaza you didn’t say how you solved the problem!

It would be helpful for other users who may be having the same issue, and are searching for the solution.

 

 

[dufaza]

Hi Andrew,

yes, you’re right, i must help others to understand ths issue.

As you know, i’m using MKBP with some BLEMLC code, modified for my specific application.

So, i tried to increase/decrease the RF ouput power of the STM32WB07KC chip (BlueNRG-LP) with the  aci_hal_set_tx_power_level function.

But in this code (originally BLEMLC) there is one line to fix TX power for advertising and another one to fix TX power for transmitted data … and i just changed in the past the 2nd one.

So, with my smartphone i detected principally/observe the TX power of advertising … not the other one.

So, in conclusion, i’ve no problem … the aci_hal_set_tx_power_level function works perfectly.

I also experimented PHY_LE_1M, PHY_LE_2M and also PHY_LE_CODED, all that works perfectly.

And for my application PHY_LE_CODED is very interesting since i multiply by 2-3 my BLE distance range.

Also, i may observe that the printed antenna of the STBP and the filter … etc. absorbe about 20dBm (not really certified measures). n externam ANT2 may be helpful.

I keep available if you need additional comments.

Best regards, Christian

[dufaza]

Hi Andrew,
yes, you’re right, i must help others to understand this issue.
As you know, i’m using MKBP with some BLEMLC code, modified for my specific application.
So, i tried to increase/decrease the RF ouput power of the STM32WB07KC chip (BlueNRG-LP) with the  aci_hal_set_tx_power_level function.
But in this code (originally BLEMLC) there is one line to fix TX power for advertising and another one to fix TX power for transmitted data … and i just changed in the past the 2nd one.
So, with my smartphone i detected principally/observe the TX power of advertising … not the other one.
So, in conclusion, i’ve no problem … the aci_hal_set_tx_power_level function works perfectly.
I also experimented PHY_LE_1M, PHY_LE_2M and also PHY_LE_CODED, all that works perfectly.
And for my application PHY_LE_CODED is very interesting since i multiplie by 2-3 my BLE distance range.
Also, i may observe that the printed antenna of the STBP and the filter … etc. absorbe about 20dBm (not really certified measures). An external ANT2 may be helpful.
I keep available if you need additional comments.
Best regards, Christian

[Alex911]

Thanks for posting the solution. The clarification about changing the TX power for advertising versus transmitted data is very helpful. I can see how that could lead to confusing test results when measuring signal strength with a smartphone.

Your observations on PHY_LE_CODED are also valuable. Thanks for sharing your findings with the community.