SolidSense AIOT - MCU

Software Flashing and Usage

MCU Firmware Flashing

Flashing equipment

Part Name	Qty.	Picture
USB-C Cable	1
STLINK-V3	1
Micro USB-B Cable	1
ST-LINK V3 SWD/JTAG programming cable (10/20-pin adapter set)	1

The flashing process requires a local computer with the following software installed:

STM32CubeProgrammer:

STM32CubeProg | Software - STMicroelectronicsSTMicroelectronics

Aiot_accb1ab.hex

143KB

Open

Preparing the AIOT for flashing

Connect STLINK-V3 (CN5) to the computer via micro USB. Connect the AIOT (J5006) to the STLINK (STDC14) using the ST-LINK V3 SWD/JTAG programming cable. Ensure that the cable is connected to the AIOT in the correct orientation, as shown in the image.

Connect the AIOT to the computer using a USB cable.

Turn ON the AIOT using the designated switch.

Flashing the software

Open STM32CubeProgrammer:

Select Erasing & Programming from the left menu. (1)

Find the appropriate Port and connect. (2)

Load the appropriate HEX file. (3)

Verify the selections according to the image. (4)

Click Start Programming. (5)

After the successful completion message is displayed, you can proceed to the testing process.

Device Usage Guide

Overview

This project implements an I2C slave interface on the STM32U031C8 MCU to control and read multiple sensors. The MCU acts as a slave device, receiving commands from a master over I2C and performing actions such as turning sensors on/off, reading sensor data, and configuring thresholds.

Supported sensors and modules

LED

Infrared (IR) sensor

Accelerometer

GPS

Battery charger status

Real-time clock (RTC)

Interrupts (MCU, IR, ACC)

Command Definitions:

Core/Inc/protocol.h

Command & Response Format:

Command structure: | CMD (1B) | SENSOR_ID (1B) | DATA_LEN (1B) | DATA (N Bytes) |

Response structure: | STATUS (1B) | DATA_LEN (1B) | DATA (N Bytes) |

examples:

busAdd=1

devAddr=0x18

Command Description	Command	Expected Response	example
Turn ON LED	{ 0x10, 0x01, 0x00, {} }	{ 0x00, 0x00, {} }	i2ctransfer -y $busAdd "w3@$devAddr" 0x10 0x01 0x00 r2@$devAddr
Turn OFF LED	{ 0x11, 0x01, 0x00, {}}	{ 0x00, 0x00, {} }	i2ctransfer -y $busAdd "w3@$devAddr" 0x11 0x01 0x00 r2@$devAddr
Read IR data	{ 0x12, 0x02, 0x00 ,{} }	{ 0x00, 5, {INT, int16 presenceVal, int16 motionVal} }	i2ctransfer -y $busAdd "w3@$devAddr" 0x12 0x02 0x00 r7@$devAddr
Set IR threshold	{ 0x13, 0x02, 0x01, {THS} }	{ 0x00, 0x00, {}}	i2ctransfer -y $busAdd "w4@$devAddr" 0x13 0x02 0x01 THS r2@$devAddr
Read acceleration	{ 0x12, 0x03, 0x00, {} }	{ 0x00, 1, {INT} }	i2ctransfer -y $busAdd "w3@$devAddr" 0x12 0x03 0x00 r3@$devAddr
Set ACC threshold	{ 0x13, 0x03, 0x01, {THS} }	{ 0x00, 0x00, {} }	i2ctransfer -y $busAdd "w4@$devAddr" 0x13 0x03 0x01 THS r2@$devAddr
Read battery status	{ 0x12, 0x05, 0x00 ,{} }	{ 0x00, 3, {power_source, battery_soc, charge_status} }	i2ctransfer -y $busAdd "w3@$devAddr" 0x12 0x05 0x00 r5@$devAddr
Read current time	{ 0x12, 0x06, 0x00 ,{} }	{ 0x00, 6, {YY,MM,DD,HH,MM,SS} }	i2ctransfer -y $busAdd "w3@$devAddr" 0x12 0x06 0x00 r8@$devAddr
Synchronize RTC with GPS	{ 0x13, 0x06, 0x00, {} }	{ 0x00, 0x00, {} }	i2ctransfer -y $busAdd "w3@$devAddr" 0x13 0x06 0x00 r2@$devAddr
Read MCU/IR/ACC interrupts	{ 0x12, 0x07, 0x00, {} }	{ 0x00, 3, {MCU, IR, ACC} }	i2ctransfer -y $busAdd "w3@$devAddr" 0x12 0x07 0x00 r5@$devAddr

Sensor Thresholds & Configuration:

Accelerometer

Interrupt code:

Code	Meaning
0x00	No motion detected
0x01	Motion detected

Default threshold: ACC_THS_DEFAULT = 0x04

Trigger values: 0–63 (1 LSB = fraction of ±2g full scale)

Threshold (mg) = FS(g) × (threshold / 64) × 1000

Threshold	FS(g) = ±2g (mg)
1	31 mg
2	62 mg
4	125 mg
8	250 mg
16	500 mg
32	1 g
63	1.97 g

Recommended values:

1–3: Very sensitive (tiny motion)

4–8: Medium motion (walking, light shake)

10–20: Strong motion (hit, fall)

Infrared Sensor (IR)

Interrupt code:

Code	Meaning
0x00	No motion detected
0x02	Motion detected
0x04	Presence detected

Frequency [Hz]= 1Hz = 1000ms Hysteresis Default (HYST = 32)

Detection:

Compares two internally filtered signals

Event flag set if difference > threshold

Flag cleared when signal < (threshold − hysteresis)

Threshold	Hysteresis	Approx. Signal Change	Use Case
100	32	≥0.05°C	Very sensitive, long range
150	32	≥0.075°C	Sensitive, moderate range
200	32	≥0.1°C	Balanced sensitivity/stability
250	32	≥0.125°C	Less sensitive, shorter range
300	32	≥0.15°C	Low sensitivity, short range
400	32	≥0.2°C	Minimal sensitivity, very stable

Battery Charging

Power Source Code	Meaning
000b	Not powered from VBUS
100b	Unknown adapter
111b	Boost OTG

Charge Status Code	Meaning
000	Not charging
001	Trickle charge
010	Pre-charge
011	Fast charge (CC mode)
100	Taper charge (CV mode)
110	Top-off timer active charging
111	Charge termination done