Set the desired radio parameters by checking the appropriate radio button from Prelude's Mode panel. The radio parameters of each selection are defined below.
In NoMac mode, the transmit power is always set to the highest power available from the module.
Time on Air
The LoRa physical layer allows many combinations of low-level parameters like the spreading factor (SF), bandwidth and coding rate (CR). These parameters affect the data rate, sensitivity, and time on air. In NoMac mode, Prelude limits selection or radio parameters to the three options listed in the table below. Each selection represents a trade-off between data rate and link margin.
Prelude allows several operating frequency bands: 868.5 - 868.6 MHz; 868.7 - 869.2 MHz; 869.4 - 869.65 MHz; 869.7 - 870 MHz; and 902 - 928 MHz. The entire LoRa transmission must fit within any one of the listed frequency bands.
Clicking the Set Frequency button sets the center frequency of the LoRa transmission. If the selected radio parameters are incompatible with the selected frequency, Prelude will issue a warning similar to the following:
To open the Transmit Window, click the Show Transmit button.
Prelude will repeatedly transmit the same message if the Repeat check box is selected. Prelude will send the message, wait one second, and then attempt to transmit again. If the module is still transmitting the previous message, Prelude will wait another second and then attempt to transmit again. This process repeats until either the Stop button is clicked or the Repeat check box is de-selected.
Click the Start Receiving button to begin receiving messages sent from other NoMac-mode modules. Prelude will write the selected radio parameters to the module before it sets the module to receive. Upon receipt of a message, the module sets the IRQ_FLAGS_RX_DONE flag. Prelude then retrieves the message from the module and displays the message in the Receive Window.
The module is able to receive any LoRa transmissions with matching radio parameters.
A module using NoMac provides a special operating mode called Echo mode. In Echo mode assigns a module to be either a master or slave node. The master node initiates an echo transaction by transmitting a LoRa message. The slave node receives the transmission from the master and then promptly echos by transmitting the same message. The master node then attempts to receive the echo from the slave node.
To use Echo mode, attach an evaluation board to Prelude and select Options > Set Remote Echo Mode. This configures the attached module to be a slave node.
Enter the desired message in the Message edit box and click Transmit.
Select the RF path
Setting the RF path is done in the same way for NoMac and Symphony Link modes.
Switching to Symphony Link mode
To switch Prelude to control the module using Symphony Link mode, select Options > Symphony Link. The NO_MAC Prelude form will close and a new Symphony Prelude form will open.
While in NoMac mode, Prelude's logging functionality is identical to that in Symphony Link mode.