Nordic distance toolbox example

Background

Nordic has released Nordic Distance Toolbox and some sample apps in Nordic Connect SDK.

Although it's possible to use the examples, I'm more of a barebone guy. With the NDT, it's possible to get the I and Q tones from the multi-carrier phase difference measurement, and thus, it's possible to play with them.

For example, estimating the impulse response between two devices

python3 py/plot.py impulse --com /dev/tty.usbmodem0006857014091

Expected knowledge

This repository assume you know a few things, like

• git
• C
• Python programming and how to get missing packages with python3 -m pip install
• installing NRF Connect SDK
• Basics of communcation

Getting started

You need Nordic Connect SDK

• Via the nRF Connect for Desktop open the Toolchain manager
• Install latest NRF Connect SDK. This repo is tested with v2.1.0
• In the Toolchain Manager, open command prompt
• In the command prompt, make sure the environment is loaded, for example c:\ncs\v2.0.0\zephyr\zephyr-env.cmd
• Try the steps below. If you don't have make, then you can look in the Makefile for the commands, for example

    cd reflector
    west build -b nrf52833dk_nrf52833 -- -DCONF_FILE=prj.conf

Once everything is installed, then you should be able to do

make first

And look in the Makefile for the rest

How it works

The code is made for nRF52833DK, so you need two of those.

The reflector code (reflector/src/main.c) must be flashed to one kit

make flashr

The initiator code (initiator/src/main.c) must be flashed to another kit

make flashi

The initiator will wait for a character on UART (any character). Then, it will execute a ranging procedure, and afterwards dump json version of the nrf_dm_report_t to the terminal

{"i_local": [0, 0, 0, 0, -7319, -7313, 4926, -6128, -316, -6474, 7072, -4938, -6043, 6389, 6451, 1381, -43, 1325, -5936, 5771, -2543, 294, 1164, -2840, -2087, 1769, 5671, -721, 3287, 2414, 3323, -2681, 502, -3325, 4849, 4444, -4889, 401, -4510, -4476, 3529, -3800, -4655, -912, -2990, -1097, 103, 4481, 4393, 1313, 2873, -363, -2859, -3791, -3363, -3471, 4228, -3889, 3721, -1410, 2003, 3972, -1836, -4289, 4037, -4360, -2153, 4321, -4289, 1402, -3008, 3359, -1563, -4496, -4156, 3462, -4343, 4222, 4669, 0], "q_local": [0, 0, 0, 0, -364, -61, 5351, 3895, -7200, 3021, -467, -5019, -3498, 2597, -2164, 6584, -6651, 6433, 2540, 2679, -5738, 6155, -5974, 5254, -5507, 5512, 187, -5556, -4430, 4817, -4196, 4518, -5164, -3922, 1418, -2230, -715, -4866, -1788, -1699, -3170, -2773, 154, 4517, 3464, -4430, 4527, -75, 790, -4252, 3371, 4407, -3372, -2217, -2750, 2586, 945, -1886, 2135, -4063, -3829, 1589, -3897, 405, 1644, 232, 3838, 924, -1293, 4290, 3400, -3106, 4343, -1094, 2077, -3096, 1719, 2030, -728, 0], "i_remote": [0, 0, 0, 0, 5710, 5989, -7324, 3591, 3350, 5030, -6847, 5855, 6503, -6543, -6564, -464, -1542, 438, 6411, -4283, -300, 3063, -4365, 5485, -2258, 2487, -3862, -3738, -5358, 2812, -5129, 5100, -4618, -2281, -600, -3515, 853, -4604, -651, -749, -3645, -2250, 347, 4398, 3497, -4295, 4352, 430, 1171, -3933, 3643, 4112, -3764, -2842, -3281, 1332, 2355, -3110, 3499, -4108, -2476, 3362, -4141, -1953, 3553, -2523, 1715, 3466, -3766, 3917, -91, 1166, 993, -4326, -2630, 1970, -3471, 4563, 4217, 0], "q_remote": [0, 0, 0, 0, 5040, 4644, 1654, 6545, -6608, 5305, -2380, -4142, -2668, 2403, -2024, 6733, -6474, 6522, 296, 4674, -6221, 5276, -4122, 2141, -5334, 5117, 4011, -4005, -187, 4442, 762, -196, -2027, -4395, 4849, 3287, -4688, -1033, -4621, -4555, 2730, -3930, -4468, -576, -2671, -932, -1, 4328, 4128, 1713, 2240, -1044, -1951, -3124, -2609, -3957, 3450, -2756, 2266, 603, 3341, 2447, 338, -3732, 2254, -3444, -3951, 2590, -2201, -2038, -4478, 4345, -4428, -1417, -3742, 4171, -3030, -869, 1984, 0], "ifft[mm]": 1096, "phase_slope[mm]": 1522, "rssi_openspace[mm]": 501, "best[mm]": 1096, "link_loss[dB]": 34, "rssi_local[dB]": 27, "rssi_remote[dB]": 26, "txpwr_local[dB]": 8, "txpwr_remote[dB]": 8, "quality": 0}

The py/plot.py can read the JSON directly from device, or from file to produce plots.

python3 py/plot.py impulse --com /dev/tty.usbmodem0006857014091

Examples

Collect some data. In the attached dataset I placed one DK on my Roomba iRobot, and the other stationary, and let the collection run for a while

python3 py/plot.py msave --com /dev/tty.usbmodem0006857014091 data/irobot --count 100

python3 py/plot.py impulsedir data/irobot

All the data from that run is in data/irobot

Support

Don't expect any, but at the same time, don't be afraid to ask.

Changelog

• Fixed high_precision_calc
• Updated to nRF Connect SDK v2.1.0
• Added hopping sequence
• Added duration

Known issues

• You need to set the sid_refl and sid_init in the Makefile to the correct ID's for your dev-kits
• On windows I've seen problems with the common/src/dm.c . That's included with a symbolic link, and that does not always work on Windows. The solution is to copy the common/src/dm.c file to the reflector/src/ and initiator/src/ directory

Wanted features

If you feel like it, fork and send pull requests. I would like the following future features

Support for multiple reflectors

Today the AA is hardcoded in initiator and reflector, however, it should be possible to use the buttons on the DK to change the AA. One way to do it could be

• On Reflector. On button press, increment the AA
• On Initiator. On button press, increment the number of AA's the initiator would loop through

Low power reflector

The reflector would be battery powered, right now it camps on a frequency and waits for a packet from initiator. If it times out, it will restart the radio, and camp again. This draws mA of current.

One option would be to setup BLE advertizing on the reflectors with a low advertizing interval, for example 4 seconds. The initiator could scan for advertiziers. Once it sees an advertizer it could respond, and wake the reflector. The reflector could stay on for maybe 10 seconds or more, to make sure that the inititator could do the ranging.

This is similar, but not the same, as is done in the nrf_dm example.