DShot Protocol Specification

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Overview

DShot (Digital Shot) is a digital protocol for communication between flight controllers and ESCs. Unlike PWM-based protocols, DShot transmits discrete values with error checking, eliminating calibration requirements and providing consistent throttle resolution.

Packet Structure

Each DShot frame consists of 16 bits:

| 11-bit Throttle | 1-bit Telemetry | 4-bit CRC |
|  S S S S S S S S S S S  |        T        | C C C C |
     MSB              LSB

Throttle (bits 15-5): 11-bit value (0-2047)
Telemetry (bit 4): Request telemetry from ESC (1 = request, 0 = no request)
CRC (bits 3-0): 4-bit checksum for error detection

Throttle Value Ranges

Range	Purpose
0	Disarmed / Motor Stop
1-47	Special Commands (see below)
48-2047	Throttle (2000 resolution steps)

DShot Speed Variants

Variant	Bitrate	T1H (µs)	T0H (µs)	Bit Period (µs)	Frame Length (µs)	Max Update Rate
DShot150	150 kbit/s	5.00	2.50	6.67	106.72	~9.4 kHz
DShot300	300 kbit/s	2.50	1.25	3.33	53.28	~18.8 kHz
DShot600	600 kbit/s	1.25	0.625	1.67	26.72	~37.5 kHz
DShot1200	1200 kbit/s	0.625	0.313	0.83	13.28	~75.3 kHz

Bit Encoding

Each bit is encoded by the duration of the HIGH portion of the pulse:

Bit "1": HIGH for 75% of bit period (T1H)
Bit "0": HIGH for 37.5% of bit period (T0H)

The ratio between T1H and T0H is always 2:1.

PIO Clock Frequency Calculation

For RP2040 PIO implementation with 8 clock cycles per bit:

PIO_frequency = bitrate × 8

Variant	PIO Frequency
DShot150	1,200,000 Hz
DShot300	2,400,000 Hz
DShot600	4,800,000 Hz
DShot1200	9,600,000 Hz

RP2040 PIO Implementation Example

The RP2040/RP2350 PIO (Programmable I/O) subsystem can generate precise DShot waveforms in hardware. Here's the MicroPython implementation from driver/dshot_pio.py:

@asm_pio(sideset_init=PIO.OUT_LOW, out_shiftdir=PIO.SHIFT_LEFT, autopull=True, pull_thresh=16)
def dshot():
    wrap_target()
    label("start")
    out(x, 1)            .side(0)    [1]  # 2 cycles: shift bit into X, pin LOW
    jmp(not_x, "zero")   .side(1)    [2]  # 3 cycles: if X=0 goto "zero", pin HIGH
    jmp("start")         .side(1)    [2]  # 3 cycles: (X=1 path) stay HIGH, loop
    label("zero")
    jmp("start")         .side(0)    [2]  # 3 cycles: (X=0 path) go LOW, loop
    wrap()

Decorator Configuration

Parameter	Value	Purpose
`sideset_init`	`PIO.OUT_LOW`	Output pin starts LOW
`out_shiftdir`	`PIO.SHIFT_LEFT`	Bits shift out MSB first
`autopull`	`True`	Auto-refill output shift register when empty
`pull_thresh`	`16`	Trigger autopull after 16 bits consumed

PIO Instructions Explained

Instruction	Purpose
`wrap_target()`	Loop start marker (program jumps here after `wrap()`)
`wrap()`	Loop end marker (automatically jumps to `wrap_target()`)
`label("name")`	Creates a named jump target
`out(x, 1)`	Shifts 1 bit from output shift register into X scratch register
`jmp(condition, "label")`	Conditional or unconditional jump
`.side(n)`	Side-set: controls output pin simultaneously with main instruction
`[n]`	Delay: adds n extra clock cycles after instruction

Waveform Generation

Each bit takes exactly 8 clock cycles, achieving the required duty cycles:

Bit "1" (75% duty cycle):          Bit "0" (37.5% duty cycle):
        ┌──────────────┐                   ┌──────┐
        │   6 cycles   │                   │  3   │
        │     HIGH     │ 2 cycles          │ HIGH │   5 cycles
────────┘              └───LOW───  ────────┘      └─────LOW─────

Execution path for bit = 1:

out(x,1).side(0)[1] → 2 cycles, pin LOW, X=1
jmp(not_x,"zero").side(1)[2] → 3 cycles, pin HIGH, condition false (X≠0)
jmp("start").side(1)[2] → 3 cycles, pin HIGH, loop back

Execution path for bit = 0:

out(x,1).side(0)[1] → 2 cycles, pin LOW, X=0
jmp(not_x,"zero").side(1)[2] → 3 cycles, pin HIGH, jumps to "zero"
jmp("start").side(0)[2] → 3 cycles, pin LOW, loop back

CRC Calculation

Standard DShot

// value = (throttle << 1) | telemetry_bit
crc = (value ^ (value >> 4) ^ (value >> 8)) & 0x0F;

Bidirectional DShot (inverted CRC)

crc = (~(value ^ (value >> 4) ^ (value >> 8))) & 0x0F;

Packet Assembly

Take 11-bit throttle value (0-2047)
Shift left by 1 bit, OR with telemetry bit: (throttle << 1) | telemetry
Calculate 4-bit CRC
Combine: (throttle_with_telemetry << 4) | crc
Result is 16-bit packet, transmitted MSB first

Arming Sequence

ESCs require an arming period before accepting throttle commands:

Send throttle value 0 continuously
Duration varies by firmware (typically 300ms for Bluejay)
After arming, ESC accepts throttle values 48-2047

Special Commands (0-47)

Commands Requiring Motors Stopped

Code	Command	Repeat	Wait After
0	MOTOR_STOP	-	-
1	BEEP1	1x	260ms
2	BEEP2	1x	260ms
3	BEEP3	1x	260ms
4	BEEP4	1x	280ms
5	BEEP5 (extended)	1x	1020ms
6	ESC_INFO	1x	12ms
7	SPIN_DIRECTION_1	6x	-
8	SPIN_DIRECTION_2	6x	-
9	3D_MODE_OFF	6x	-
10	3D_MODE_ON	6x	-
11	SETTINGS_REQUEST	-	Not implemented
12	SAVE_SETTINGS	6x	35ms
13	EDT_ENABLE (Extended Telemetry)	6x	-
14	EDT_DISABLE	6x	-
20	SPIN_DIRECTION_NORMAL	6x	-
21	SPIN_DIRECTION_REVERSED	6x	-
22	LED0_ON	1x	-
23	LED1_ON	1x	-
24	LED2_ON	1x	-
25	LED3_ON	1x	-
26	LED0_OFF	1x	-
27	LED1_OFF	1x	-
28	LED2_OFF	1x	-
29	LED3_OFF	1x	-
30	AUDIO_STREAM_MODE	-	Not implemented
31	SILENT_MODE	-	Not implemented
32	SIGNAL_LINE_TELEMETRY_DISABLE	6x	-
33	SIGNAL_LINE_TELEMETRY_ENABLE	6x	-
34	SIGNAL_LINE_CONTINUOUS_ERPM_TELEMETRY	6x	-
35	SIGNAL_LINE_CONTINUOUS_ERPM_PERIOD_TELEMETRY	6x	-

Telemetry Request Commands (Can Be Sent Anytime)

Code	Command	Resolution	Max Value
42	TEMPERATURE_TELEMETRY	1°C per LSB	4095°C
43	VOLTAGE_TELEMETRY	10mV per LSB	40.95V
44	CURRENT_TELEMETRY	100mA per LSB	409.5A
45	CONSUMPTION_TELEMETRY	10mAh per LSB	40.95Ah
46	ERPM_TELEMETRY	100 eRPM per LSB	409,500 eRPM
47	ERPM_PERIOD_TELEMETRY	16µs per LSB	65,520µs

Bidirectional DShot

Bidirectional DShot enables ESC-to-FC communication on the same signal wire, primarily for eRPM telemetry.

Requirements

DShot300 or higher (DShot150 not supported)
Compatible ESC firmware (BLHeli_32, BLHeli_S with Bluejay/JESC, AM32)
Signal line must support bidirectional communication

Signal Inversion

Bidirectional DShot uses inverted signal levels:

Standard: HIGH = 1, LOW = 0
Bidirectional: HIGH = 0, LOW = 1

The inverted CRC signals to the ESC that bidirectional mode is active.

Timing

|<-- FC Transmit -->|<-- Gap -->|<-- ESC Response -->|
     16 bits           ~30µs         21 bits (GCR)

FC transmits 16-bit command
~30µs gap for line turnaround
ESC responds with 21-bit GCR-encoded eRPM frame

eRPM Response Frame

The ESC returns a 16-bit value encoded using GCR (Group Code Recording):

12-bit eRPM data: 3-bit exponent + 9-bit mantissa
4-bit CRC

GCR encoding expands 16 bits to 21 bits for improved noise immunity.

GCR Decoding

gcr_decoded = value ^ (value >> 1);

eRPM Calculation

period_us = mantissa << exponent;  // in microseconds
erpm = 60000000 / period_us;       // electrical RPM
rpm = erpm / (motor_poles / 2);    // mechanical RPM

Extended DShot Telemetry (EDT)

Modern alternative to separate telemetry wire. Uses eRPM frame bandwidth to transmit additional data:

Temperature
Voltage
Current
Debug values

Supported by: Bluejay, BLHeli_32, AM32

ESC Compatibility

ESC Firmware	DShot150	DShot300	DShot600	DShot1200	Bidirectional
BLHeli_S (EFM8BB1)	✓	✓	✗	✗	✗
BLHeli_S (EFM8BB2/BB21)	✓	✓	✓	✓	With Bluejay/JESC
BLHeli_32	✓	✓	✓	✓	✓
KISS	✓	✓	✓	✓	✓
AM32	✓	✓	✓	✓	✓

Implementation Notes

Signal Integrity

Higher DShot rates are more susceptible to noise
DShot600 is the most commonly used variant (balance of speed and reliability)
Use short signal wires and proper grounding
Consider DShot150/300 for long cable runs

Timing Accuracy

Bit timing must be within ±10% tolerance
PIO-based implementations provide precise timing
Software bit-banging may struggle at DShot600+

Update Rate

Send throttle commands continuously (typically every 1-2ms)
ESCs may shut down if no valid command received within timeout
Bidirectional mode roughly halves effective update rate due to response wait

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DShot Protocol Specification

Overview

Packet Structure

Throttle Value Ranges

DShot Speed Variants

Bit Encoding

PIO Clock Frequency Calculation

RP2040 PIO Implementation Example

Decorator Configuration

PIO Instructions Explained

Waveform Generation

CRC Calculation

Standard DShot

Bidirectional DShot (inverted CRC)

Packet Assembly

Arming Sequence

Special Commands (0-47)

Commands Requiring Motors Stopped

Telemetry Request Commands (Can Be Sent Anytime)

Bidirectional DShot

Requirements

Signal Inversion

Timing

eRPM Response Frame

GCR Decoding

eRPM Calculation

Extended DShot Telemetry (EDT)

ESC Compatibility

Implementation Notes

Signal Integrity

Timing Accuracy

Update Rate

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DShot Protocol Specification

Overview

Packet Structure

Throttle Value Ranges

DShot Speed Variants

Bit Encoding

PIO Clock Frequency Calculation

RP2040 PIO Implementation Example

Decorator Configuration

PIO Instructions Explained

Waveform Generation

CRC Calculation

Standard DShot

Bidirectional DShot (inverted CRC)

Packet Assembly

Arming Sequence

Special Commands (0-47)

Commands Requiring Motors Stopped

Telemetry Request Commands (Can Be Sent Anytime)

Bidirectional DShot

Requirements

Signal Inversion

Timing

eRPM Response Frame

GCR Decoding

eRPM Calculation

Extended DShot Telemetry (EDT)

ESC Compatibility

Implementation Notes

Signal Integrity

Timing Accuracy

Update Rate