Hi Nordic Support Team,
I'm currently experimenting with Channel Sounding using a couple of nRF54L15 boards.
I am trying to obtain raw I and Q samples so that I may analyze it on my computer.
To do so I modified the example Bluetooth: Channel Sounding Initiator with Ranging Requestor to print the I/Q samples out to the console. I changed the function `ranging_data_get_complete_cb` as follows:
static void ranging_data_get_complete_cb(struct bt_conn* conn, uint16_t ranging_counter, int err) {
ARG_UNUSED(conn);
if (err) {
LOG_ERR("Error when getting ranging data with ranging counter %d (err %d)", ranging_counter, err);
return;
}
LOG_DBG("Ranging data get completed for ranging counter %d", ranging_counter);
/* This struct is static to avoid putting it on the stack (it's very large)
*/
static cs_de_report_t cs_de_report;
cs_de_populate_report(&latest_local_steps, &latest_peer_steps, BT_CONN_LE_CS_ROLE_INITIATOR, &cs_de_report);
net_buf_simple_reset(&latest_local_steps);
net_buf_simple_reset(&latest_peer_steps);
k_sem_give(&sem_local_steps);
cs_de_quality_t quality = cs_de_calc(&cs_de_report);
for (uint8_t ant_path = 0; ant_path < cs_de_report.n_ap; ant_path++) {
for (uint8_t tone = 0; tone < 80; tone++) {
printk("%u %u %f %f %f %f\n", procedure_number, tone, (double)cs_de_report.iq_tones[0].i_local[tone],
(double)cs_de_report.iq_tones[0].q_local[tone], (double)cs_de_report.iq_tones[0].i_remote[tone],
(double)cs_de_report.iq_tones[0].q_remote[tone]);
}
}
procedure_number++;
if (quality == CS_DE_QUALITY_OK) {
for (uint8_t ap = 0; ap < cs_de_report.n_ap; ap++) {
if (cs_de_report.tone_quality[ap] == CS_DE_TONE_QUALITY_OK) {
store_distance_estimates(&cs_de_report);
}
}
}
}
When run, this is the output that is produced:
0 0 -27.000000 -40.500000 19.500000 -55.500000 0 1 8.666664 -35.999996 -32.999996 -27.333328 0 2 56.666668 7.000000 -74.000000 18.333332 0 3 74.000000 -30.666664 -92.666664 -12.000000 0 4 9.666660 -70.666664 -37.999992 -57.333332 0 5 100.000000 35.000000 -110.000000 53.000000 0 6 -105.000000 -6.000000 108.000000 -57.000000 0 7 -103.000000 19.000000 120.000000 10.000000 0 8 65.500000 80.500000 -42.500000 106.000000 0 9 44.000000 -99.000000 -67.000000 -109.000000 . . [Omitting several lines for clarity] . 0 71 42.333328 34.333332 -84.666664 -10.999996 0 72 -34.000000 -45.500000 58.500000 -22.000000 0 73 -99.500000 13.500000 101.000000 55.500000 0 74 0.333332 -32.999996 3.666666 -40.333328 0 75 0.000000 0.000000 0.000000 0.000000 0 76 0.000000 0.000000 0.000000 0.000000 0 77 0.000000 0.000000 0.000000 0.000000 0 78 0.000000 0.000000 0.000000 0.000000 0 79 0.000000 0.000000 0.000000 0.000000
Where the first number is `procedure_number` (corresponds to the number of times `ranging_data_get_complete_cb` was called), the second number is the `tone` index and the other 4 are `i_local`, `q_local`, `i_remote` and `q_remote`, respectively.
I have several questions based on observing the data:
Question 1:
What units are `i_local`, `q_local`, `i_remote` and `q_remote` measured in? I have assumed that it is in degrees, but I cannot find any indication of this in include/bluetooth/cs_de.h.
Question 2:
Why are some of the readings of `i_local`, `q_local`, `i_remote` and `q_remote` measured as 0?