Skip to content

[Sponsored by FlightWave] Enable more than one DShot timer on STM32H7 #26013

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Open
wants to merge 4 commits into
base: main
Choose a base branch
from
Open

[Sponsored by FlightWave] Enable more than one DShot timer on STM32H7 #26013

wants to merge 4 commits into from
+101 −70

Conversation

@julianoes
Copy link
Contributor

@julianoes julianoes commented Nov 28, 2025 •
edited
Loading

This extends DShot and Bidirectional DShot to more than one timer.

So far I have tested this on a CubeOrange with 6 outputs (AUX 1-4 on timer 1, AUX 5-6 on timer 4).

nsh> dshot status
INFO  [dshot] Outputs initialized: yes
INFO  [dshot] Outputs used: 0x3f
INFO  [dshot] Outputs on: yes
dshot: cycle: 41433 events, 1187949us elapsed, 28.67us avg, min 24us max 150us 2.546us rms
dshot: bdshot rpm: 20718 events
dshot: dshot telem: 0 events
INFO  [mixer_module] Param prefix: PWM_AUX
control latency: 41433 events, 9900016us elapsed, 238.94us avg, min 228us max 491us 7.134us rms
INFO  [mixer_module] Switched to rate_ctrl work queue
Channel Configuration:
Channel 0: func: 101, value: 109, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 1: func: 102, value: 317, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 2: func:   0, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 3: func:   0, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 4: func: 103, value: 430, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 5: func: 104, value: 676, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
INFO  [arch_dshot] dshot driver stats:
INFO  [arch_dshot] Bidirectional DShot enabled on 2 timer(s)
INFO  [arch_dshot] Output 0: eRPM 172, read 19816, failed nibble 0, failed CRC 0, invalid/zero 902
INFO  [arch_dshot] Output 1: eRPM 426, read 19817, failed nibble 0, failed CRC 0, invalid/zero 902
INFO  [arch_dshot] Output 2: eRPM 0, read 0, failed nibble 0, failed CRC 0, invalid/zero 0
INFO  [arch_dshot] Output 3: eRPM 0, read 0, failed nibble 0, failed CRC 0, invalid/zero 0
INFO  [arch_dshot] Output 4: eRPM 581, read 19817, failed nibble 0, failed CRC 0, invalid/zero 903
INFO  [arch_dshot] Output 5: eRPM 845, read 19822, failed nibble 0, failed CRC 0, invalid/zero 902

@julianoes
dshot: extend to more than 1 timer for STM32H7
2cb0d98 
This extends dshot and bidir dshot to more than one timer.
@julianoes
dshot: improve status output
f7eabf5 
This now shows the channels in output order rather than timer channel
order, and while at it, shows the actual eRPM read.
@julianoes julianoes requested a review from dakejahl November 28, 2025 01:37
@github-actions
Copy link

github-actions bot commented Nov 28, 2025 •
edited
Loading

🔎 FLASH Analysis

px4_fmu-v5x [Total VM Diff: 1588 byte (0.07 %)] 
    FILE SIZE        VM SIZE    
--------------  -------------- 
[ = ]       0  +1.6% +1.38Ki    .bss
  [ = ]       0  +400%   +1024    dshot_capture_buffer
  [ = ]       0  [NEW]    +160    _cc_calls
  [ = ]       0  +400%     +64    read_fail_crc
  [ = ]       0  +400%     +64    read_fail_nibble
  [ = ]       0  +400%     +64    read_fail_zero
  [ = ]       0  +320%     +64    read_ok
  [ = ]       0 +11e2%     +11    _bidirectional
  [ = ]       0  [NEW]      +5    _bidi_timer_indices
  [ = ]       0  [NEW]      +3    _num_bidi_timers
  [ = ]       0  [DEL]     -19    [section .bss]
  [ = ]       0  [DEL]     -32    _cc_call
+0.0%    +176  +0.0%    +176    .text
   +18%     +76   +18%     +76    dma_burst_finished_callback
   +38%     +56   +38%     +56    up_bdshot_status
  +6.1%     +32  +6.1%     +32    capture_complete_callback
  [NEW]     +24  [NEW]     +24    CSWTCH.58
   +42%     +16   +42%     +16    DShot::update_num_motors()
  [NEW]     +12  [NEW]     +12    up_bdshot_set_active_channels
  -1.5%      -4  -1.5%      -4    build_gam_response()
  -0.6%      -4  -0.6%      -4    up_dshot_init
  -0.0%      -8  -0.0%      -8    [section .text]
  [DEL]     -24  [DEL]     -24    CSWTCH.62
+0.1%      +4  +0.1%      +4    .data
  [NEW]      +4  [NEW]      +4    _bdshot_active_channels
+0.0%     +65  [ = ]       0    .debug_abbrev
+0.0%      +8  [ = ]       0    .debug_aranges
+0.0%     +36  [ = ]       0    .debug_frame
+0.0%    +493  [ = ]       0    .debug_info
+0.0%    +126  [ = ]       0    .debug_line
  [DEL]      -1  [ = ]       0    [Unmapped]
  +0.0%    +127  [ = ]       0    [section .debug_line]
+0.0%    +171  [ = ]       0    .debug_loclists
+0.0%     +92  [ = ]       0    .debug_rnglists
+0.0%     +81  [ = ]       0    .debug_str
+0.0%     +92  [ = ]       0    .strtab
  [NEW]     +10  [ = ]       0    CSWTCH.58
  [DEL]     -10  [ = ]       0    CSWTCH.62
 -44.4%     -16  [ = ]       0    __sched_lock_veneer
   +59%     +16  [ = ]       0    __stm32_dmaresidual_veneer
  [NEW]     +24  [ = ]       0    _bdshot_active_channels
  [NEW]     +20  [ = ]       0    _bidi_timer_indices
  [DEL]      -9  [ = ]       0    _cc_call
  [NEW]     +10  [ = ]       0    _cc_calls
  [NEW]     +17  [ = ]       0    _num_bidi_timers
  [NEW]     +30  [ = ]       0    up_bdshot_set_active_channels
+0.0%    +144  [ = ]       0    .symtab
  [NEW]     +32  [ = ]       0    CSWTCH.58
  [DEL]     -48  [ = ]       0    CSWTCH.62
 -40.0%     -32  [ = ]       0    __sched_lock_veneer
   +67%     +32  [ = ]       0    __stm32_dmaresidual_veneer
  [NEW]     +32  [ = ]       0    _bdshot_active_channels
  [NEW]     +32  [ = ]       0    _bidi_timer_indices
 -33.3%     -16  [ = ]       0    _bidirectional
  [DEL]     -32  [ = ]       0    _cc_call
  [NEW]     +32  [ = ]       0    _cc_calls
  [NEW]     +48  [ = ]       0    _num_bidi_timers
   +50%     +16  [ = ]       0    read_fail_nibble
 -25.0%     -16  [ = ]       0    up_bdshot_channel_status
  [NEW]     +64  [ = ]       0    up_bdshot_set_active_channels
-1.6%    -176  [ = ]       0    [Unmapped]
+0.0% +1.28Ki  +0.1% +1.55Ki    TOTAL
px4_fmu-v6x [Total VM Diff: 1656 byte (0.08 %)] 
    FILE SIZE        VM SIZE    
--------------  -------------- 
[ = ]       0  +1.5% +1.44Ki    .bss
  [ = ]       0  +400%   +1024    dshot_capture_buffer
  [ = ]       0  [NEW]    +160    _cc_calls
  [ = ]       0  +400%     +64    read_fail_crc
  [ = ]       0  +400%     +64    read_fail_nibble
  [ = ]       0  +400%     +64    read_fail_zero
  [ = ]       0  +320%     +64    read_ok
  [ = ]       0  +123%     +59    [section .bss]
  [ = ]       0  [NEW]      +5    _bidi_timer_indices
  [ = ]       0  [NEW]      +3    _num_bidi_timers
  [ = ]       0 -75.0%      -3    _bidirectional
  [ = ]       0  [DEL]     -32    _cc_call
+0.0%    +184  +0.0%    +184    .text
   +18%     +80   +18%     +80    dma_burst_finished_callback
   +38%     +56   +38%     +56    up_bdshot_status
  +6.1%     +32  +6.1%     +32    capture_complete_callback
  [NEW]     +24  [NEW]     +24    CSWTCH.59
   +42%     +16   +42%     +16    DShot::update_num_motors()
  [NEW]     +12  [NEW]     +12    up_bdshot_set_active_channels
  -0.6%      -4  -0.6%      -4    up_dshot_init
  -0.0%      -8  -0.0%      -8    [section .text]
 -50.0%     -24 -50.0%     -24    CSWTCH.63
+0.0%     +65  [ = ]       0    .debug_abbrev
+0.0%      +8  [ = ]       0    .debug_aranges
+0.0%     +36  [ = ]       0    .debug_frame
+0.0%    +477  [ = ]       0    .debug_info
+0.0%    +162  [ = ]       0    .debug_line
  +300%      +3  [ = ]       0    [Unmapped]
  +0.0%    +159  [ = ]       0    [section .debug_line]
+0.0%    +286  [ = ]       0    .debug_loclists
+0.0%     +97  [ = ]       0    .debug_rnglists
 -33.3%      -1  [ = ]       0    [Unmapped]
  +0.0%     +98  [ = ]       0    [section .debug_rnglists]
+0.0%     +81  [ = ]       0    .debug_str
+0.9%      +2  [ = ]       0    .shstrtab
+0.0%    +102  [ = ]       0    .strtab
  [NEW]     +10  [ = ]       0    CSWTCH.59
  [NEW]     +24  [ = ]       0    _bdshot_active_channels
  [NEW]     +20  [ = ]       0    _bidi_timer_indices
  [DEL]      -9  [ = ]       0    _cc_call
  [NEW]     +10  [ = ]       0    _cc_calls
  [NEW]     +17  [ = ]       0    _num_bidi_timers
  [NEW]     +30  [ = ]       0    up_bdshot_set_active_channels
+0.0%    +144  [ = ]       0    .symtab
  [NEW]     +32  [ = ]       0    CSWTCH.59
 -60.0%     -48  [ = ]       0    CSWTCH.63
  [NEW]     +32  [ = ]       0    _bdshot_active_channels
  [NEW]     +32  [ = ]       0    _bidi_timer_indices
 -33.3%     -16  [ = ]       0    _bidirectional
  [DEL]     -32  [ = ]       0    _cc_call
  [NEW]     +32  [ = ]       0    _cc_calls
  [NEW]     +48  [ = ]       0    _num_bidi_timers
   +50%     +16  [ = ]       0    read_fail_nibble
 -25.0%     -16  [ = ]       0    up_bdshot_channel_status
  [NEW]     +64  [ = ]       0    up_bdshot_set_active_channels
-2.6%    -184  [ = ]       0    [Unmapped]
+0.0% +1.43Ki  +0.1% +1.62Ki    TOTAL

Updated: 2025-11-29T01:07:57

@julianoes
dshot: don't try to read inactive channels
36f66aa 
If there is no ESCs connected on a timer channel, we don't need to go
through it when doing the round robin eRPM read.
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@dakejahl dakejahl Awaiting requested review from dakejahl

At least 1 approving review is required to merge this pull request.

Assignees

No one assigned

Labels

None yet

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

2 participants

@julianoes