✅ Open the nrf52-code/radio-app/src/bin/radio-send.rs file.
✅ First run the program radio-send.rs as it is. You should see new output in the output of cargo xtask serial-term, if you left your Dongle on channel 20. If you change your Dongle's channel to avoid interference, change to the channel to match in radio-send.rs before you run it.
$ cargo xtask serial-term
deviceid=588c06af0877c8f2 channel=20 TxPower=+8dBm app=loopback-fw
received 5 bytes (CRC=Ok(0xdad9), LQI=53)The program broadcasts a radio packet that contains the 5-byte string Hello over channel 20 (which has a center frequency of 2450 MHz). The loopback program running on the Dongle is listening to all packets sent over channel 20; every time it receives a new packet it reports its length and the Link Quality Indicator (LQI) metric of the transmission over the USB/serial interface. As the name implies the LQI metric indicates how good the connection between the sender and the receiver is (a higher number means better quality).
Because of how our firmware generates a semihosting exception to tell our flashing tool (probe-run) when the firmware has finished running, if you load the radio-send firmware and then power-cycle the nRF52840-DK, the firmware will enter a reboot loop and repeatedly send a packet. This is because nothing catches the semihosting exception and so the CPU reboots, sends a packet, and then tries another semihosting exception.