Understanding channel select on radio test example

[Tandon]

Hello Nordic team,

I am trying to get my product read for FCC/CE compliance testing. I came across the radio_test example and other examples posted on DevZone. I have the following queries.

1) The Test lab wants me to test the product in 2402MHz, 2442MHz , 2480MHz. They want me to transmit in these frequencies separately. In the example channel is set to sweep from 0 to 80. Is it safe to assume that 0 is LOW; 40 is MED and 80 is HIGH? I am planning on doing a single channel sweep using 

radio_tx_carrier(txpower_, mode_, channel);
radio_tx_sweep_start(txpower_, mode_, channel, channel, delayms_);

txpower_ and mode_ are the default values. 

2) I do not have a spectrum analyzer, the infocenter piece explains that we can use a another board with the same example. Would this be in  rx_sweep mode? i am not very familiar with RF just yet so the more information provided would help me greatly.

Appreciate your time,

Tandon 

[Andreas]

Hi,

 

1. The sweep function is not quite what they are after, they are after a way to set the transmitter to 2402 MHz, 2440 MHz and 2480 MHz. The radio test example comes with a UART CLI that lets you configure this through a terminal, no reason to worry about the source code. Of course you could make separate images that set up the transmitter upon startup, it is all up to what you and the test house prefer.

2. No the receiver would need to run the start_rx command, with the same bitpattern, mode and on the same channel. You then need to use the start_tx_modulated_carrier or start_duty_cycle_modulated_tx on your DUT. You do not need to do this though, the transmitter just needs to transmit 'something', so you might find the RSSI App in nRF Connect for Desktop more convenient to prove this (this uses your 2nd DK as a makeshift spectrum analyzer).

 

Best regards,

Andreas

[Tandon]

Thanks for the lighting quick response,

1) I am planning on using GPIOTE button in order to jump through the channels instead of UART. What line of code should I use to set the transmit channel? Where my assumptions correct for the channels?

[Tandon]

I am guessing its radio_modulated_tx_carrier correct? How can I set the separate channels? 

[Andreas]

Yes, either radio_modulated_tx_carrier or radio_unmodulated_tx_carrier, depending on if you want modulated carrier or not. The channel is determined when you call the function, as an example:

void radio_modulated_tx_carrier(RADIO_TXPOWER_TXPOWER_Pos4dBm, RADIO_MODE_MODE_Ble_1Mbit, 40)

will start the radio on channel 40, in BLE 1Mbps mode at 4 dBm. Changing the frequency by pushing a button takes some work, you need to add that to the GPIOTE button event handler.

 

Best regards,

Andreas