Regarding setting Tx power to +8dbm

RE: Regarding setting Tx power to +8dbm

Ravi Theja — Tue, 23 Jul 2019 09:02:02 GMT

Ok, Hung, I will work on it. Thanks for the support.

RE: Regarding setting Tx power to +8dbm

Hung Bui — Tue, 23 Jul 2019 08:54:24 GMT

It's not possible to estimate the range without actual measurements and tests. Many factors can affect the actual range.

RE: Regarding setting Tx power to +8dbm

Ravi Theja — Tue, 23 Jul 2019 05:17:38 GMT

Hi Hung,

If it supports 100m distance with +4dBm, then power requirements also less. Thanks for the suggestion. But my application requires devices may not be in the line of sight and surrounded by metals. So, I am thinking of using +8dBm to meet the requirements. Will +8dBm works for my application?

I don't have nRF52 DK right now. I will try to get it and test on it.

RE: Regarding setting Tx power to +8dbm

Hung Bui — Mon, 22 Jul 2019 12:00:16 GMT

You don't need +8dBm for 100m distance if your device is properly tune and if light of sight, out door. +4dBm should be enough. Make sure you device is properly tuned. We would suggest you to test using our nRF52 DK.

RE: Regarding setting Tx power to +8dbm

Ravi Theja — Mon, 22 Jul 2019 11:23:02 GMT

Ok awneil. Thank you.

My application requires Tx and Rx are 100m apart needs to be connected and data transmission should happen. But with current power setting Tx and Rx are not getting connected. So, I am trying to understand whether I am utilizing total Tx power or not.

RE: Regarding setting Tx power to +8dbm

awneil — Mon, 22 Jul 2019 11:15:03 GMT

[quote userid="81871" url="~/f/nordic-q-a/50090/regarding-setting-tx-power-to-8dbm/199741"]there is a change in RSSI[/quote]

That's the best you can do without proper test equipment.

But, to be honest, how will measuring the number help?

RE: Regarding setting Tx power to +8dbm

Ravi Theja — Mon, 22 Jul 2019 11:06:42 GMT

Hi awneil,

Is there any other to verify it without RF analyzer? because I don't have it right now.

yeah, there is a change in RSSI signal when I change the power setting from -8dbm to +8dbm.

RE: Regarding setting Tx power to +8dbm

awneil — Mon, 22 Jul 2019 10:34:59 GMT

There will always be losses. An RSSI of -15dBm sounds pretty good.

[quote userid="81871" url="~/f/nordic-q-a/50090/regarding-setting-tx-power-to-8dbm/199729"]Is there any way to know whether peripheral is transmitting 8dbm signal or not[/quote]

you would need a proper RF analyser.

Remember that the +8dBm figure is the output from the chip itself; so it will be affected by your PCB layout, antenna, and antenna tuning - before it even leaves your board!

You can verify that you code is actually having an effect by changing between, say, +8 and -8 ...

RE: Regarding setting Tx power to +8dbm

Ravi Theja — Mon, 22 Jul 2019 10:23:35 GMT

Hi awneil,

When I place the mobile near the device, Mobile should receive almost the same signal strength transmitted by peripheral?

Is there any way to know whether peripheral is transmitting 8dbm signal or not?

RE: Regarding setting Tx power to +8dbm

awneil — Mon, 22 Jul 2019 10:16:22 GMT

[quote userid="81871" url="~/f/nordic-q-a/50090/regarding-setting-tx-power-to-8dbm"]when i see the RSSI signal in mobile using nRF connect for mobile app its showing maximum of -15dbm instead of +8dbm[/quote]

Of course you won't see +8dBm !

"RSSI" = Received Signal Strength Indication - it is what your phone is receiving - not what the peripheral is transmitting!

RE: Regarding setting Tx power to +8dbm

Ravi Theja — Mon, 22 Jul 2019 10:08:05 GMT

Hi awneil, Thanks for the quick reply.

I am placing +8 based on the API description.

/**@brief Set the radio's transmit power.
 *
 * @param[in] role The role to set the transmit power for, see @ref BLE_GAP_TX_POWER_ROLES for
 *                 possible roles.
 * @param[in] handle   The handle parameter is interpreted depending on role:
 *                     - If role is @ref BLE_GAP_TX_POWER_ROLE_CONN, this value is the specific connection handle.
 *                     - If role is @ref BLE_GAP_TX_POWER_ROLE_ADV, the advertising set identified with the advertising handle,
 *                       will use the specified transmit power, and include it in the advertising packet headers if
 *                       @ref ble_gap_adv_properties_t::include_tx_power set.
 *                     - For all other roles handle is ignored.
 * @param[in] tx_power Radio transmit power in dBm (see note for accepted values).
 *
  * @note Supported tx_power values: -40dBm, -20dBm, -16dBm, -12dBm, -8dBm, -4dBm, 0dBm, +2dBm, +3dBm, +4dBm, +5dBm, +6dBm, +7dBm and +8dBm.
  * @note The initiator will have the same transmit power as the scanner.
 * @note When a connection is created it will inherit the transmit power from the initiator or
 *       advertiser leading to the connection.
 *
 * @retval ::NRF_SUCCESS Successfully changed the transmit power.
 * @retval ::NRF_ERROR_INVALID_PARAM Invalid parameter(s) supplied.
 * @retval ::BLE_ERROR_INVALID_ADV_HANDLE Advertising handle not found.
 * @retval ::BLE_ERROR_INVALID_CONN_HANDLE Invalid connection handle supplied.
 */
SVCALL(SD_BLE_GAP_TX_POWER_SET, uint32_t, sd_ble_gap_tx_power_set(uint8_t role, uint16_t handle, int8_t tx_power));

RE: Regarding setting Tx power to +8dbm

awneil — Mon, 22 Jul 2019 09:57:36 GMT

rc = sd_ble_gap_tx_power_set( BLE_GAP_TX_POWER_ROLE_ADV , m_adv_handle, +8 );

Are you sure that "+8" is the correct way to specify the power?

What does the documentation say ... ?

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