drop_detect

Soldering iron drop-triggered shield for real time embedded systems university course (firmware).

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Table of Contents

• drop_detect
  • 1 Overview
    • 1.1 Bill of Materials (BOM)
    • 1.2 Block Diagram
    • 1.3 Pin Configurations
    • 1.4 Clock Configurations
  • 2 Software Logic
    • 2.1 Scheduling (FreeRTOS vs Cyclic Executive)
  • 3 Real Time Analysis
    • 3.1 Setup
    • 3.2 Install Python (pip) Packages
    • 3.3 Running the Code
  • 4 Third-Party Licenses

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1 Overview

Free fall triggered shield and impact detection example.

1.1 Bill of Materials (BOM)

Manufacturer Part Number	Manufacturer	Description	Quantity	Notes
STM32L432KC	STMicroelectronics	32-bit MCU	1
WS2812B	(Various)	PWM Addressable RGB LED	1
BNO085 or BNO086	CEVA Technologies, Inc.	9-DOF IMU	1

1.2 Block Diagram

Drawio file here: drop_detect.drawio.

1.3 Pin Configurations

CubeMX Pinout

Pin & Peripherals Table

STM32L432KC	Peripheral	Config	Connection	Notes
PB3	SYS_JTDO-SWO		Onboard ST-Link
PA14	SYS_JTCK-SWCLK		Onboard ST-Link
PA13	SYS_JTMS-SWDIO		Onboard ST-Link
	TIM2_CH1	PWM no output		Scheduler, BNO085 SH2 driver timer.
PA5	SPI1_SCK		BNO085 Pin 19: H_SCL/SCK/RX
PA4	GPIO_Output (SPI1 CS)	Set high	BNO085 Pin 18: H_CSN
PA6	SPI1_MISO		BNO085 Pin 20: H_SDA/H_MISO/TX
PA7	SPI1_MOSI		BNO085 Pin 17: SA0/H_MOSI
PB0	GPIO_EXTI0	Pull-up, falling edge	BNO085 Pin 14: H_INTN
PB1	GPIO_Output	Set high	BNO085 Pin 6: PS0/Wake	Pull low to trigger wake.
		Hardware pull-up	BNO085 Pin 5: PS1
PA1	GPIO_Output	Set high	BNO085 Pin 11: NRST	Pull low to reset.
PA8	TIM1_CH1	PWM Generation CH1	WS2812B Pin: DIN	DIN pin number depends on IC variant.
PC15	GPIO_Output	Pull-down, set low	GPIO	General trigger pin, active high.

1.4 Clock Configurations

8 MHz High Speed External (HSE)
 -> Phase-Locked Loop Main (PLLM)
 -> 80 MHz SYSCLK
 -> 80 MHz HCLK
     -> 80 MHz APB1 (Maxed) -> 80 MHz APB1 Timer
     -> 80 MHz APB2 (Maxed) -> 80 MHz APB2 Timer

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2 Software Logic

2.1 Scheduling (FreeRTOS vs Cyclic Executive)

Two scheduling configurations can be utilized:

1. FreeRTOS implemented and configured with STM32CubeMX.
2. A basic cyclic executive hardware timer based scheduler.

Option 1 (FreeRTOS) is utilized for scheduling by default.

Found within configuration.h is the configuration macro:

#define DROP_DETECT_USE_FREERTOS 1

By changing this macro from 1 to 0, the cyclic executive scheduler is enabled and FreeRTOS initialization and operation is disabled.

Note: The SYS Timebase Source is set to TIM16 in order to free SysTick for the FreeRTOS kernal.

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3 Real Time Analysis

To support additional real time analysis a python statistical script (real_time_analysis.py) was created, found in python.

The script accepts a .csv file of raw logic analyser data exported from Saleae Logic 2 for a single channel.

Saleae is a trademark of the respective owners. Use of these names does not imply any endorsement by the trademark holders.

3.1 Setup

• Assumes python environment is already setup (Python 3.10 or newer).

3.2 Install Python (pip) Packages

• Install packages your preferred way. If using pip, use the generic command below with requirements.txt:

pip install -r requirements.txt

3.3 Running the Code

The main code can be run right off of main.py:

python real_time_analysis.py

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4 Third-Party Licenses

This project uses the following open-source software components:

• CEVA sh2, CEVA Inc.

  • Licensed under the Apache License, Version 2.0.
    • See NOTICE.txt and code headers, for example in: sh2.h.

• STM32Cube HAL, STMicroelectronics.

  • Licensed under the 3-Clause BSD License.
    • See LICENSE.txt.

CEVA and STMicroelectronics are trademarks of their respective owners. Use of these names does not imply any endorsement by the trademark holders.