JN516x Transmit Power control

[NestorFernandes]

I want to fine tune the transmit power of JN516x for testing purposes in smaller steps than those allowed by function vJPT_RadioSetPower. Is there another function available or any document describing the registers that control the TX power?

[mario_castaneda]

Hi Nestor,

Please follow the next post.

https://community.nxp.com/thread/455276 

Hope it helps.

Regards,

Mario

[NestorFernandes]

Hi Mario,

Thank you for your reply, but I still need help.

Let me explain what I need in more detail. I designed a board with JN5168 and a PA+LNA from Skyworks that can boost the transmit power in 20 dBm flat. That means that if I transmit with 0 dBm at the TX output of JN5168 the PA will boost the signal to +20 dBm, give or take.

The PA is being controlled by JN5168 as it should be, but now I need to map all possible steps of transmit power for the board. The functions that allow me to set the transmit power for JN5168 are too coarse, so I'd like to know:

1) can you guys share the information about the internal JN5168 register that sets the transmit power?

2) is there any hidden (not documented) function that can set the transmit power for JN5168 in smaller (finer) steps?

3) the docs mention that we can change the transmit power in 32 steps (5 bits), but only 4 or 5 steps are available. Why is that?

Thank you,

-- Nestor

[davidashraf]

Hello Nestor , 

Can you please tell me how do you - currently - control the transmit power ?

Regards
David

[NestorFernandes]

Hi David,

I have two scenarios: one for testing only (using a special firmware from NXP) and one for communication (ZigBee 3.0 stack).

The testing set is the same described in JN-AN-1122. The firmware provided by NXP has the 4 levels limitation of the complete stack.

The ZigBee 3.0 stack firmware I'm using allows me to get 4 steps. My code is:

#define RADIO_TX_POWER            (-9)         // dBm

//=============================================================================
//! \brief Set radio power.
//=============================================================================

void Set_Radio_Power (void)
{
    DBG_PRINTF_INFO ("Enabling PA+LNA and adjusting PA input to %d dBm\n", RADIO_TX_POWER);

    // Enable PA+LNA

    vAHI_HighPowerModuleEnable(TRUE, TRUE);

    // Set JN5168 radio power output to -9 dBm

    eAppApiPlmeSet(PHY_PIB_ATTR_TX_POWER, (uint32_t)RADIO_TX_POWER);
}

The document JN-UG-3087 says:

• 2.2.1 Transmission Power
  The radio transmission power of a JN516x device can be varied. To set the
  transmission power, you can use the function eAppApiPlmeSet()from the NXP
  802.15.4 Stack API (supplied in AppApi.hin all the JN516x SDKs). The required
  function call is:
        eAppApiPlmeSet(PHY_PIB_ATTR_TX_POWER, x);
  where x is a 6-bit two’s complement power level, corresponding to an input range of
  -32 to 31 dBm. In practice, this value is mapped to an actual transmission level:
• For JN5168, JN5164 and JN5161, it is mapped to one of four levels:
  -32, -20, -9 and 0 dBm
• For JN5169, it is mapped to the nearest of 26 levels in the range -32 to 10 dBm
  Therefore, some positive input values will be truncated (to 10 dBm for the JN5169
  device and to 0 dBm for the other JN516x devices).

My board has a +20 dBm PA flat. If I set the JN5168 to 0 dBm, I get +20 dBm (give or take) at the antenna. I need to control the power to achieve +18 dBm, +16 dBm, and so on. The function described above gives me the choice to have at the antenna only +20 dBm, +13 dBm, 0 dBm (-20 from JN5168 and + 20 from PA).

That's ridiculous. I cannot effectively control the transmit power - and by extension the consumption profile - of my board.

With access to the internal register that controls the output TX power of JN5168, I can fine tune my board. I know there is a register and I guess the guys who designed the chip would put more than 2 bits for controlling the TX power in that register (the doc says 6 bits - 64 steps).

I just couldn't figure out why they decided to give away only 4 steps - that are meaningless for effective power control.

Regards,

-- Nestor

[NestorFernandes]

Just to close this thread:

The limitation described above is not in the stack or software libraries, but in the silicon of JN5168. Its internal transmit power control circuit has only 4 steps of 12 dBm each, so you cannot set anything between +3 dBm and -9 dBm, for instance. No transmit power fine tune.

Too bad...

-- Nestor

[mario_castaneda]

Hi Nestor,

Unfortunately, we do not have a register map document for the radio in the JN5168.

There are only four power levels on the JN5168 and that is it. I suggest to move to the JN5169 where there are 64 power levels. The software should just recompile in the same environment and the PCB modifications are minimal.

Regards,

Mario

[vinitmehta]

Hi Mario,

Will it be possible for you to share the register map table for JN5169 chipset? 

In order to control the output power we need the register map control or power mapping levels with which we can make sure appropriate steps which is available for JN5169 and can set the power accordingly.

It would be really helpful if you can direct me to a document or information regarding this.

Thanks

Vinit

[mario_castaneda]

Hi Vinit,

Please see the file attached and look at the 

IEEE 802.15.4 Stack User Guide v2.6 3.8.1 Transmission Power

Hope it helps

Regards,

Mario