CC2642R: TI Launchpad and Host Test: Chnaging TX power level using HCIExt_SetTxPowerCmd to 0dBm and 5dBM does not show any difference

If you use spectrum analyzer to do conductive test, does it show difference ?

No, spectrum analyzer as well dors not show any difference  as well. Note that I am using sdk 3.10. I assume the next revision does not have any issue like this addressed.

SDK 3.10 is pretty old and I suggest you to test with latest SDK 4.10.

Are you sure that v4.10 is available? I believe that the latest version is 3.40 only. Can you confirm?

Also, are you sure that such issue on the Host Test firmware has been resolved recently in SDK releases or this is just your best guess?

Yes, it's available at SIMPLELINK-CC13X2-26X2-SDK

Even after using the SDK v3.40, it is same result.

Request you to take this request up in urgent manner.

I test with the following steps and I can see RSSI changes.

1. Send HCIExt_EndModemTestCmd.

2. Send HCIExt_SetTxPowerCmd to change TX power.

3. Send HCIExt_ModemTestTxCmd to check TX power.

I am following same steps.

How does your setup look like? Are you using spectrum analyzer?

Which version of SDK are you using?

Can you give your resdings in here for various power level set?

I don't have spectrum analyzer nearby now so  I use SmartRF Studio 7 continuous RX to check RSSI. I use prebuilt HostTest firmware in SDK 4.10. When I set TX power to HCI_EXT_TX_POWER_MINUS_21_DBM, I see -42dbm on RSSI. When I set TX power to  HCI_EXT_TX_POWER_0_DBM, I see -32~-34dbm on RSSI. When I set TX power to  HCI_EXT_TX_POWER_5_DBM, I see -30~-31dbm on RSSI.

By the way, two of my test LAUNCHXL-CC26X2R1 are close to each other.

You keep refering to SDK v4.10. But for CC26x2 platform is 3.40. Can you confirm?

Also, RSSI value of -31dBm to -33dBm for 0dBm and 5dBm is expected? I was expecting a difference of at least 5 dBm here.

Also, can you give us some understanding on what should be the expectation for 0dBm and 5dBm in spectrum analyzer?

I just test the same thing on SDK 3.40 prebuilt HostTest and I see similar results. Even you do a conductive test using spectrum analyzer, you cannot expect see 5 dbm in RSSI when you set TX to 5 dbm. There is always cable lose when doing the test. If you do radiation test, the lose would be much larger.

No, I am not expecting 5dBm RSSI level. But I am expecting at least 5 dBm difference in RSSI for 0dBm and 5dBm transmit power.

It won't be linear.

So, you aresaying that difference in RSSI for 2 to 3 dBm for trasmit power of 0 dBm and 5 dBm is valid?

Also, is there any graph on trasnmit power v/s expected RSSI values?

When I see RSSI difference to differnt TX power, I would say it's normal. I don't have any graph on trasnmit power v/s expected RSSI values since there are too many factors to affect this.

Well, I am still seeing that the RSSI value for transmit power 0dBm and 5dBm alre almost same with +/- 1dBm. How can we ensure that the behavior is really changin?

What RSSI do you see exactly when you set TX power to 0dBm and 5dBm?

They are almost flat and same for both 0dBm and 5dBm as I have indicated in my graph taken from Smart RF studio above.

RSSI value stays at -31/-32dBm for for both.

If you set TX power to -21 dbm, does RSSI decrease?

Yes, you can see that in my graph as well. RSSI is -37dBm when the transmit power is set to -12dBm.

But my conetntion over here is why there is no change I can really see for 0dBm and 5dBm transmit power.

Since you cannot see big difference with radiation test on SmartRF Studio, I can only suggest you to use spectrum analyzer to do conductive test.

Hi,

To verify if the TxPower has been properly modified, I suggest to perform a power consumption analyze. The power consumption is significantly modified when passing from 0dBm to 5dBm.

I suggest the following App Note to help you.

Best regards,

We are using the conductive test setup only. That means that we should see a visible difference for 0dBm and 5dBm.

Not that the same hardware we are using with Smart RF Studio (one as transmit and one as receive), we are seeing the visible difference. While using the BTool and HCI APIs for changing the transmit power and tranmitter test, the power appears not changed at all.

This has become a painful for us now. It looks like that the Host Test tool with the BTool is not working as expected.

Mehul

There’s one tricky thing to be noted. If you select channel 0 in HCIExt_ModemTestTxCmd, it stands for BLE advertising channel 37 which is 2402 MHz. So, make sure you measure correctly on your SmartRF Studio or spectrum analyzer.

Nope, I have configured the channel correctly for 0th channel (i.e. 2404 MHz in Smart RF).

Which channel do you set in HCIExt_ModemTestTxCmd?

Channel 0 with havin receive channel set to 2404 MHz

When I select channel 0 in HCIExt_ModemTestTxCmd, it stands for BLE advertising channel 37 which is 2402 MHz.

I am setting channel 1 in HCIExt_ModemTestTxCmd() API i.e. 2404 MHz. And Channel 0 in Smart RF studio while setting up board for BLE.

I just test channel 1 in HCIExt_ModemTestTxCmd()  and Channel 0 in Smart RF studio. I see the same results as I test with channel 0 in HCIExt_ModemTestTxCmd()  and Channel 37 in Smart RF studio.

Can you elaborate on what does it mean by same result?

When I test channel 1 in HCIExt_ModemTestTxCmd()  and Channel 0 in Smart RF studio. I set TX power to HCI_EXT_TX_POWER_MINUS_21_DBM, I see -42dbm on RSSI. When I set TX power to  HCI_EXT_TX_POWER_0_DBM, I see -32~-34dbm on RSSI. When I set TX power to  HCI_EXT_TX_POWER_5_DBM, I see -30~-31dbm on RSSI. This is the same to my previous test When I test channel 0 in HCIExt_ModemTestTxCmd()  and Channel 37 in Smart RF studio.

I have found the root issue.

Looks like SDK v3.10 and v3.20 which we are using for our firmware development from where the Host Test fimrware is used rejects setting up transmit power using HCIExt_SetTXPowerCmd  API with transmit power set to 3/4/5dBm.

After that, if I try using the HOs Test from SDK v3.40 and v4.10, the issue seems fixed and I am able to set the transmit power to 5 dBm and see the difference in RSSI as well.

The change log from v3.40 and v4.10 does not suggest any issue like that have been fixed (at lest that is not something I have found). Can you point towards the issue resolution in these SDK?

Yet, I would like to understand what it would take to resolve this issue in v3.10 as our BLE peripheral firmware is based on that and we would like to keep the Host Test firmware as well from the same SDK.

Thanks for your support so far!!!

SDK 3.10 is obsolete. If possible, I would suggest you to upgrade to SDK 4.10.