CC2642R: How to change transmit power of advertisment

I am going to try this out. However, can you comment on above questions on why default value does not work and where in the source code can be changed for the default transmit power?

According to http://software-dl.ti.com/lprf/ble5stack-docs-latest/docs/ble5stack/ble_user_guide/doxygen/ble/html/struct_gap_adv__params__t.html , txPower in this data strict is not implemented . You should use HCI_EXT_SetTxPowerCmd to set TX power.

I agree with above comment. But then why DEFAULT_TX_POWER in ble_user_config.c did not work? It worked for simple peripheral application without using 

HCI_EXT_SetTxPowerCmd()

How do you check TX power after you set different DEFAULT_TX_POWER in ble_user_config.c?

I am having two BLE peripheral running on LPs. One is Simple Peripheral example and second has my own BLE application. I am using NRF Connect application in my mobile to check the RSSI value from both. The Simple Peripheral reflects the RSSI value changed based on default TX power. But having the similar change in my own application does not get reflected in RSSI graph in the mobile application. I have tried -20dBm to 5 dBm.

Hello Chen,

I have called HCI_EXT_SetTxPowerCmd(HCI_EXT_TX_POWER_5_DBM) and also checked that its status is HCI_SUCCESS once returned. Yet, the change did not reflect in RSSI. In fact, I can see that the TX Power always remains to -20dBm. When I set this transmit power -20dBm in simple peripheral example, I can see that both of them have same RSSI values.

is your own application based on simple_peripheral example? If so, I see no reason why you get inconsistent results.

Hi Mehul,

Try this and see if there are any changes HCI_EXT_SetTxPowerCmd(5);. 

-kel

One more update. I was trying to place this HCI_EXT_SetTxPowerCmd() on various locations in my code. I finally found that if this call is made in the GAP_EVT_ADV_END event handler in the application, then only I see that the transmit power really gets changed. But I have call this HCI_EXT_SetTxPowerCmd() each time on GAP_EVT_ADV_END. This does not look quite right. The API works in that case but I am very doubtful on why this API must be called on every single GAP_EVT_ADV_END.

Hello YiKai,

I have a changing advertisement data set. Above code I have tired was with disabling the data set change. After advertising data set changes, even calling HCI_EXT_SetTxPowerCmd() does not work at any place in the code which handles various advertisement related events.

Can you tell me in which conditions this transmit power can be changed by the ble stack internally itself.?

That did not work as well. ll.h file under C:\ti\simplelink_cc13x2_26x2_sdk_4_20_01_04_s\source\ti\ble5stack\controller\cc26xx\inc suggests that value 5 is -9dBm.

Hello Mehul,

Can you try using the HCI_LE_ReadTxPowerCmd() API to verify what the set power is after using the HCI_EXT_SetTxPowerCmd()? When you say it doesn't work do you mean to say that when you use the HCI_LE_ReadTxPowerCmd() the power did not change? You should be able to easily change it any time during runtime as shown in the E2E thread link earlier.

Regards,

Jan

Mehul Dalal said:

5 is -9dBm

Ah okay sorry that was from my CC2640R2F Beacon project.

I suppose the correct way to call HCI_EXT_SetTxPowerCmd() is during init or after you disable advertisement. I do not have test equipment to verify this so I am not sure.

-kel

Okay, I will try this as well.

But can you tell me under what circumstances the BLE stack itself changes the transmit power for the advertisements from the default one set?

Hello,

I have gone through the HCI_LE_ReadTxPowerCmd(), but it just gives min and max transmit power can be supported, not the current transmit power set. How that would be helpful here?

Mehul

Hi Mehul,

I apologize for the confusion, I meant to use HCI_ReadTransmitPowerLevelCmd(). This should give you the current transmit power.

Regards,

Jan

Can you provide some example on using this API? How does it return the current transmit power? It is not clear from the documentation. Also, what should I set for txPwrType ?

Hi Mehul,

The following E2E thread goes in-depth into how to use HCI_ReadTransmitPowerLevelCMD():  https://e2e.ti.com/support/wireless-connectivity/bluetooth/f/bluetooth-forum/839904/ccs-cc2640r2f-ccs-cc2640r2f-set-txpower-failed-with-cmd-hci_ext_settxpowercmd-and-read-failed-with-cmd-hci_le_readtxpowercmd/3106652

Regards,

Jan

I have called this API in the firmware.

HCI_ReadTransmitPowerLevelCmd(0, HCI_READ_CURRENT_TX_POWER_LEVEL);

I am getting HCI_READ_TRANSMIT_POWER event from the stack and then parsing the data.  I am not sure which index in the return parameter of HCI_READ_TRANSMIT_POWER event gives the actual transmit power set. But I have read first 4 indices and their values are as below:

Transmit Power Read pMsg->pReturnParam[0] = 0
Transmit Power Read pMsg->pReturnParam[1] = 0
Transmit Power Read pMsg->pReturnParam[2] = 0
Transmit Power Read pMsg->pReturnParam[3] = 24

Which index gives the transmit power read?

The issue here is setting the actual TXPower and not reading the value set using a C function or API.

Mehul, I suppose you also need better way to check if the TXPower has changed by using test equipment specific for measuring TXPower. A change in current consumption also indicates a change in TXPower.

-kel

I am not sure what do you really meant on HCI_READ_TRANSMIT_POWER above.

Whichever transmit power I set, the energy consumption using EnergyTrace utility in CCS always have the same current consumption level during advertisment.

From my CC2640R2F Eddystone Beacon project below I am able to set TXPower 0 dBM and 5 dBM indicated by a change in current consumption using EnergyTrace. There was an issue with setting the TXPower which I applied a simple workaround to resolve. But that is for CC2640R2F and long time ago. 

https://markelthinkslearnscreates.wordpress.com/2018/10/23/ti-cc2640r2f-eddystone-beacon/

-kel

Okay, I am going through it. But Can you suggest when HCI_READ_TRANSMIT_POWER event is received, which index in pReturnParam gives the transmit power set?

Also, I believe that the discussion is going no where now. i am trying different ways as suggested and also I am ready to try out different ways as well. But, can someone please suggest how to move forward?

Can you elaborate how to parse the received event data in HCI_READ_TRANSMIT_POWER ?

Hi Mehul,

You mentioned that you are able to properly change the TX transmit value in simple_peripheral, but not in your project. Is your project based on simple peripheral or is it based on a different example? I mentioned using HCI_ReadTransmitPowerLevelCmd earlier to verify if the stack changes the transmit power internally after calling HCI_EXT_SetTxPowerCmd. However, Markel's suggestion of using energy trace would be a good way of verifying if there is any change in the TX power. Since you are not seeing a change in the EnergyTrace, then this tells us that there really is not change in the TX power.

However, I believe that to change the default TX power, this change should be done in SysConfig in the following field:

Can you try modifying this field and verifying if there is any change in the EnergyTrace?

Regards,

Jan

My application is base din simple peripheral but does not use SysCfg.

Hello Mehul,

I apologize, I misread your comment on Sysconfig. I did quick test of calling HCI_EXT_SetTxPowerCmd() right before the GapAdv_create() function in the GAP_DEVICE_INIT_DONE_EVENT case of the SimplePeripheral_processGapMessage() function. As shown below:

        ...
        BLE_LOG_INT_TIME(0, BLE_LOG_MODULE_APP, "APP : ---- got GAP_DEVICE_INIT_DONE_EVENT", 0);
        // Setup and start Advertising
        // For more information, see the GAP section in the User's Guide:
        // http://software-dl.ti.com/lprf/ble5stack-latest/


        // Set a different TX Power [ADDED]
        HCI_EXT_SetTxPowerCmd(HCI_EXT_TX_POWER_5_DBM);

        BLE_LOG_INT_INT(0, BLE_LOG_MODULE_APP, "APP : ---- call GapAdv_create set=%d,%d\n", 0, 0);
        // Create Advertisement set #1 and assign handle
        status = GapAdv_create(&SimplePeripheral_advCallback, &advParams1,
                               &advHandleLegacy);
        SIMPLEPERIPHERAL_ASSERT(status == SUCCESS);
        ...

By doing this I was able to measure a change in the EnergyTrace as shown below:

The following screenshot is of the unmodified simple_peripheral

The following screenshot is of the modified simple_peripheral:

When adding that line, we effectively overwrite the default TX power for the advertisements. Can you verify if the above code modification has the observed effect?

Regards,

Jan