stm32_hal_dshot

Brief

Dshot is drone ESC digital protocol

You need STM32 MCU, BLHeli_32 ESC, BLDC
STM32 MCU makes Dshot signal using PWM and DMA

KEYWORD - DSHOT BLHeli_32 ESC BLDC STM32 HAL TIMER PWM DMA

Dev Environment

• STM32CubeIDE
• STM32 HAL driver
• STM32F411
• BLHeli_32 ESC
• Drone BLDC

Library Features

• Change motor throttle
  • Throttle range : 2000 steps (0% - 100%)
• Choose Dshot 150/300/600
• Other command : no
• Telemetry : no

ESC Firmware and Protocol

ESC Firmware

	1st	2nd	3rd
ESC Firmware	BLHeli	BLHeli_S	BLHeli_32

ESC Protocol

	Analogue signal	Digital signal
ESC Protocol	PWM Oneshot125 Oneshot42 Multishot	Dshot150 Dshot300 Dshot600 Proshot1000

Dshot

1. Data Frame

• 11bits : 0 - 47 command, 48 - 2047 throttle
• 1bit : telemetry request
• 4bits : checksum

2. Bit 0 / 1

	bit 0	bit 1
duty cycle	37.425%	74.850%

3. Transmission Time

	bits / sec	sec / bit	sec / frame
Dshot150	150,000 bits/s	6.67us	106.7us
Dshot300	300,000 bits/s	3.33us	53.3us
Dshot600	600,000 bits/s	1.67us	26.7us

4. Signal Example

• throttle value : 11 / telemetry request : 0 (no) / checksum 4 bits
• 0 0 0 0 0 0 0 1 0 1 1 / 0 / 0 1 1 1

5. Arming sequence

• After power on, Send zero throttle for a while until 1 high beep is ended.
• 7p of BLHeli_32 manual ARM Rev32.x.pdf

STM32CubeMX

• Project Manager

• TIM

• DMA

Example

dshot.h

• TIM5, TIM2 is 100MHz
• MOTOR 1 - PA3
• MOTOR 2 - PA2
• MOTOR 3 - PA0
• MOTOR 4 - PA1
• Some instance are not pre-defined, so need to change in person...
  • like TIM_DMA_ID_CC4, TIM_DMA_CC4, CCR4...

/* User Configuration */
// Timer Clock
#define TIMER_CLOCK				100000000	// 100MHz

// MOTOR 1 (PA3) - TIM5 Channel 4, DMA1 Stream 3
#define MOTOR_1_TIM             (&htim5)
#define MOTOR_1_TIM_CHANNEL     TIM_CHANNEL_4

// MOTOR 2 (PA2) - TIM2 Channel 3, DMA1 Stream 1
#define MOTOR_2_TIM             (&htim2)
#define MOTOR_2_TIM_CHANNEL     TIM_CHANNEL_3

// MOTOR 3 (PA0) - TIM2 Channel 1, DMA1 Stream 5
#define MOTOR_3_TIM             (&htim2)
#define MOTOR_3_TIM_CHANNEL     TIM_CHANNEL_1

// MOTOR 4 (PA1) - TIM5 Channel 2, DMA1 Stream 4
#define MOTOR_4_TIM             (&htim5)
#define MOTOR_4_TIM_CHANNEL     TIM_CHANNEL_2

main.c

• only contain dshot things

#include "dshot.h"

// 4 motor value
uint16_t my_motor_value[4] = {0, 0, 0, 0};

int main (void)
{
    // initialize
    dshot_init(DSHOT600);

    while (1)
    {
        // transmit new dshot signals
        dshot_write(my_motor_value);
        HAL_Delay(1);
    }
}