RX enable time on the PA LNA driver for nRF21540

[Dominik Eugster]

Hi

I'm using the PA LNA driver for the nRF21540 with the function:

void mesh_lna_setup_start(uint32_t rampup_start_capture_time, uint32_t timer_index)

Now, when I check the TX and RX signals, I can see that the RX enable PIN is switched low every 200ms, not only during the TX interval.

How can I change this to 100% receiving time? When a packet is coming over BLE and the RX is switched off, this packet is getting lost.

Here is the plot of the TX, RX enable Pins:

CH1 is TX, CH2 (green) is RX:

[Mttrinh]

Hi,

Can you give more details about your setup? 

What SDK and version are you using? What example are you testing? What modifications have you made to the example?

[Mttrinh]

Hi, 

I would highly recommend you to use our nRF Connect SDK for Mesh. The examples have support for nRF21540 by default.

[Dominik Eugster]

What is the reason for this RX low every 200ms? Is it a sleep mode? This should not happen, I need RX on high-level all the time wehn TX is low.

[Mttrinh]

Hi,

I noticed you are using default configuration, this enables the GATT feature which means GATT bearer is enabled in softdevice.  To make PA\LNA work with GATT the feature should be configured separately. 

You should follow documentation here.

Can you clarify whether you keep GATT enabled and configured PA\LNA correctly for it? Have you followed the documentation?

[Dominik Eugster]

Here are the results:

CH1 (yellow) = RX enable

CH2 (green) = TX enable

What I don't understand is why RX goes low without TX is sending something, can you explain this?

[Dominik Eugster]

Mttrinh
I found a nRF21540 driver lib here:
https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsdk_nrf5_v17.0.2%2Fgroup__nrf21540.html

Should I use this one or the PA/LNA driver (which is working in my project)? I'm confused about this because until now nobody spoke about this driver.

Thanks for clarification

[Mttrinh]

Hi,

Dominik Eugster said:

What I don't understand is why RX goes low without TX is sending something, can you explain this?

Yep. This is described in the documentation that is provided.

You will see brief Active High pulses on the GPIO pin 24, which is used for the PA control. Similarly, the GPIO pin 25 (used for the LNA control) is almost always ON, except for the time when the radio switches to the next advertising channel for scanning or for sending advertisements.

You can observe that this interval of LNA Off without active TX is equal `BEARER_SCAN_INT_DEFAULT_MS` (default 2 seconds). The scanner has to change channel for scanning.

Dominik Eugster said:

I found a nRF21540 driver lib here:
https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsdk_nrf5_v17.0.2%2Fgroup__nrf21540.html

Should I use this one or the PA/LNA driver (which is working in my project)? I'm confused about this because until now nobody spoke about this driver.

If you want to use Mesh you have to follow BLE Mesh documentation recommendations. 

[Dominik Eugster]

Ok, Thank you for the information, I asked a lot of time about the Bits in the SPI protocol but nobody posted an answer about it. This driver shows exactly how the SPI communication has to be implemented, even if I use Mesh. Thanks anyway.

Reference to the post:

https://devzone.nordicsemi.com/f/nordic-q-a/85506/nrf21540-spi-communication-voltage-level-problem