This project implements a program to measure the received signal strength indication (RSSI) for the [https://decawave.com/products/dw1000](DecaWave DW1000) ultra-wideband (UWB) transceiver. The purpose of this tool is to provide a way for users to find the limits on communication range, and areas of low signal strength and reliability in environments utilizing the DecaWave DW1000.
This tool is designed to run on the DecaWave EVB1000 evaluation boards, utilizing the DW1000 UWB transceiver.
There are two programs which must be built and loaded onto the EVB1000 boards. One program continuously transmits packets, and the other program receives those packets and measures the RSSI and packet loss relative to the transmitter.
The following prerequisites are required before building the software:
- GNAT GPL 2016 for ARM ELF (available at https://libre.adacore.com/download/).
- The ravenscar-full-evb1000 runtime (available on https://github.com/damaki/ravenscar-full-evb1000).
There are two programs, a transmitter and a receiver. To build the transmitter
run the following command in the transmitter directory:
gprbuild --target=arm-eabi -Pdw1000_rssi_scan_tx.gpr
To build the receiver program run the following command in the receiver
directory:
gprbuild --target-arm-eabi -Pdw1000_rssi_scan_rx.gpr
The output of the build process described above are two executables:
transmitter/bin/dw1000_rssi_scan_tx.elf and
receiver/bin/dw1000_rssi_scan_rx.elf. These instructions to program the
STM32 microcontroller on the EVB1000 with these executables are based on the
http://www.st.com/en/development-tools/st-link-v2.html by
ST Microelectronics.
To program the executable onto the target, use the following instructions (this example programs the transmitter executable, but the process is the same for both executables, just with different file names, of course):
- Convert the ELF file to a binary (.bin) file using the following command:
arm-eabi-objcopy -Obinary dw1000_rssi_scan_tx.elf dw1000_rssi_scan_tx.bin - Connect the ST-LINK/V2 to the target EVB1000 and apply power to the board.
- Run the following command:
st-flash write dw1000_rssi_scan_tx.bin 0x08000000
Once the executables have been programmed, you can use them to measure the signal strength in your environment simply by powering on the programmed EVB1000 boards. You will need to program one EVB1000 board with the transmitter executable, and one (or more) other EVB1000 boards with the receiver executable.
The basic premise is that the transmitter transmits a continuous stream of packets using the configured channel, data rate, and PRF. The receiver(s) listens for these transmitted packets and measures the average signal strength and percentage of packets correctly received. As you move the receiver around in your environment, the signal strength and percentage of packets received will vary, allowing you to find the limits on range of the EVB1000 in your environment.
The transmitter and receiver must be configured to use the same settings (channel, data rate, and PRF). They are configured using the S1 switches at the top of the EVB1000 (to the left of the four LEDs).
Switches 3 and 4 configure the data rate:
| 3 | 4 | Data Rate |
|---|---|---|
| Off | Off | 110 kbps |
| Off | On | 850 kbps |
| On | Off | 6.81 Mbps |
| On | On | 6.81 Mbps |
Switch 5 configures the PRF:
| 5 | PRF |
|---|---|
| Off | 16 MHz |
| On | 64 MHz |
Switches 6, 7, and 8 configure the channel (frequency):
| 6 | 7 | 8 | Channel |
|---|---|---|---|
| Off | Off | Off | 1 |
| Off | Off | On | 2 |
| Off | On | Off | 3 |
| Off | On | On | 4 |
| On | Off | Off | 5 |
| On | Off | On | 7 |
| On | On | Off | 7 |
| On | On | On | 7 |
The LCD displays the current configuration on the top line, and the percentage of packets received and the average RSSI on the bottom line. An example of the information displayed is shown below:
Ch1 16MHz 110kbps
94% -93 dBm
With the above example, 94% of packets were received over the last second, and the average estimated signal strength of the received packets was -93 dBm.
If the receiver is out of range of the transmitter (or the transmitter is off, or using a different configuration), then the bottom line of the display shows dashes. For example:
Ch1 16MHz 110kbps
---% ---- dBm
The display is updated at a rate of 1 Hz, and the measurements are calculated over the previous 1 second of received packets.
Three of the LEDs on the EVB1000 are used also relay information. The behaviour of the LEDs (1 to 4, left to right) are as follows:
- Toggled every time the LCD is updated (at a rate of 1 Hz).
- Not used.
- Toggled each time a receiver error occurs (e.g. bad packet or demodulation error, etc...)
- Toggled each time a packet is received.