Correct DShot Timings

[andyp1per]

This is not really a feature request but a documentation of DShot timings for BLHeli that we should use to model our own DShot output on. BLHeli32 and BLHeli_S are incredibly sensitive to timing but always guaranteed to work on Betaflight. Here then are the betaflight timings that we should model as closely as possible

Platform

• All
• AntennaTracker
• Copter
• Plane
• Rover
• Submarine

[andyp1per]

Betaflight 4.3.0 w/DShot600 against BLHeli_S 16.7.3 (Channel 0), BLHeli32 32.7 (Channel 1) and no ESC (Channels 4 & 5). 8k gyros 1k PID loops:

Pulse-to-pulse is exactly 1ms

[andyp1per]

For Channel 0:
ΔT 26.048 µs
Nfalling 16
Nrising 16
fmin 600.962 kHz
fmax 603.865 kHz
fmean 601.54 kHz
Tstd 3.312 ns

ΔT 32.552 µs
Nfalling 1
Nrising 1

ΔT 23.92 µs
Nfalling 8
Nrising 8
fmin 266.525 kHz
fmax 435.54 kHz
fmean 345.713 kHz
Tstd 708.89 ns

For Channel 1:

First pulse is the same then

ΔT 27.616 µs
Nfalling 1
Nrising 1

ΔT 26.776 µs
Nfalling 8
Nrising 8
fmin 251.004 kHz
fmax 377.644 kHz
fmean 306.802 kHz
Tstd 760.068 ns

[andyp1per]

At 8KHz PID loop the pulse output is identical but pulse-to-pulse is 125us (i.e. 8Khz)

[andyp1per]

DShot 300 / 1Khz PIDs:

Pulse-to-pulse 1ms as before

Channel 0:
M1:
ΔT 52.112 µs
Nfalling 16
Nrising 16
fmin 300.481 kHz
fmax 301.205 kHz
fmean 300.625 kHz
Tstd 3.312 ns

M2:
ΔT 33.8 µs
Nfalling 1
Nrising 1

M3:
ΔT 50.048 µs
Nfalling 8
Nrising 8
fmin 131.441 kHz
fmax 204.918 kHz
fmean 165.188 kHz
Tstd 1.446 µs

Channel 1:
First pulse the same
M2:
ΔT 30.104 µs
Nfalling 1
Nrising 1

M3:
ΔT 53.368 µs
Nfalling 8
Nrising 8
fmin 125.502 kHz
fmax 188.253 kHz
fmean 154.104 kHz
Tstd 1.468 µs

[andyp1per]

DShot 150 / 1Khz PIDs. Interestingly BLHeli_S does not work at this point - it does not return telemetry. Also higher PID rates are disallowed because the DShot pulse will not fit:

Pulse to pulse still 1ms

M1:
ΔT 104.424 µs
Nfalling 16
Nrising 16
fmin 149.88 kHz
fmax 150.24 kHz
fmean 150.024 kHz
Tstd 4.485 ns

M2:
ΔT 34.416 µs
Nfalling 1
Nrising 1

M3:
ΔT 106.488 µs
Nfalling 8
Nrising 8
fmin 62.751 kHz
fmax 94.127 kHz
fmean 77.283 kHz
Tstd 2.887 µs

[andyp1per]

Interestingly DShot1200 is disallowed so I couldn't get any data

[andyp1per]

500Hz PID loop rate works fine so clearly ESCs do not need 1Khz as our code claims. Maybe 500Hz is the lowest - it is the lowest that Betaflight allows

[giacomo892]

Can we close this? @andyp1per