Rust firmware for IR thermometer based on STM32L151CBT6 and MLX90614.
Hardware diagram:
Notes
- No JTAG/SWD: firmware loaded using STM32 serial bootloader
- Both EEPROM (AT24) and IR sernsor (MLX90614) are connected to I2C1
Firmware diagram:
- Firmware is based on RTIC framework
- LCD driver hd44780
- MLX90614 driver mlx9061x
- AT24 EEPROM driver eeprom24x
- Independent watchdog is used to reboot system in the case of any lockup issues
- Red LED is used to indicate when battery voltage drops below 2.5V
- Green LED is used for heartbeats
- Currently Idle state has nothing to do with MCU low power modes: LCD and MLX90614 are powered off, but MCU still runs on HSI
- MLX90614 and AT24 drivers share I2C1 bus using shared-bus-rtic
Navigation through menu is performed using short button presses. Menu item selection is performed by long button presses. Menu items:
- Shot
- single temperature measurements triggered by short button presses
- ShortMem
- single temperature measurements triggered by short button presses
- each measurement is stored to EEPROM
- each new measurement session erases previous EEPROM content
- Cont
- continuous temperature measurements with 1 sec interval
- ContMem
- continuous temperature measurements with 1 sec interval
- each measurement is stored to EEPROM
- each new measurement session erases previous EEPROM content
- View
- display measurements stored in EEPROM one-by-one using short button presses
- Stream
- continuously display measurements stored in EEPROM with 1 sec interval
- stream measurements to UART to enable scripting and processing
- Battery
- single battery voltage measurements triggered by short button presses
The board does not have JTAG or SWD connector. So it has to be programmed through UART using ST bootloader. To simplify build and flash procedure, custom cargo runner is implemented. This script does the following two things:
- run
cargo-binutilsto generateihexbinary format - run
stm32flashto program device through UART
Note that BOOT0 jumper shall be properly connected to switch MCU into UART boot mode.
Custom runner calls stm32flash and llvm-objdump using certain default parameters, including baudrate, serial port, and binary format. Those changes can be modified using custom runner script input parameters:
cargo run --release --example test-led -- -h
Examples:
$ cargo run --example test-led
$ cargo run --release --example test-led
$ cargo run --example test-led -- -p /dev/ttyUSB1 -r 9600
$ cargo run --example test-led -- -t bin
Supported additional options:
Options:
-t, --type bin or ihex, default is ihex
-p, --port serial port, default is /dev/ttyUSB0
-r, --rate serial port baud rate, default is 115200
Tests and binaries support two different i2c implementations:
- i2c hardware block on stm32l1x microcontroller
- i2c software bitbang implementation
Any of the options can be selected using cargo features: i2c_hw or i2c_bb.
By default i2c_hw option is selected:
$ cargo run --release --example test-i2c-at24
$ cargo run --release --example test-i2c-mlx90614
$ cargo run --release --no-default-features --features i2c_bb --example test-i2c-at24
$ cargo run --release --no-default-features --features i2c_bb --example test-i2c-mlx90614
Use cargo-binutils to check firmware size summary:
$ $ cargo size --release --bin rust-ir-thermo
text data bss dec hex filename
48476 0 240 48716 be4c rust-ir-thermo
$ cargo size --release --example test-i2c-at24
text data bss dec hex filename
15220 0 12 15232 3b80 test-i2c-at24
Use additional option to get all sections sizes:
$ cargo size --release --bin rust-ir-thermo -- -A
rust-ir-thermo :
section size addr
.vector_table 292 0x8000000
.text 40428 0x8000124
.rodata 7756 0x8009f10
.data 0 0x20000000
.bss 124 0x20000000
.uninit 116 0x2000007c
.debug_str 48797 0x0
.debug_abbrev 3022 0x0
.debug_info 34958 0x0
.debug_aranges 1448 0x0
.debug_ranges 25584 0x0
.debug_pubnames 12771 0x0
.debug_pubtypes 342 0x0
.ARM.attributes 48 0x0
.debug_frame 4956 0x0
.debug_line 39301 0x0
.comment 147 0x0
Total 220090
Use cargo-bloat to find out what takes most of the space in firmware binary:
$ cargo bloat --release --bin rust-ir-thermo
File .text Size Crate Name
3.0% 18.8% 7.4KiB std core::fmt::float::float_to_decimal_common_shortest
2.7% 16.7% 6.6KiB std core::fmt::float::float_to_decimal_common_exact
1.7% 10.5% 4.1KiB [Unknown] EXTI2
1.2% 7.3% 2.9KiB rust_ir_thermo rust_ir_thermo::init
0.5% 3.2% 1.3KiB std <char as core::fmt::Debug>::fmt
0.4% 2.6% 1.0KiB std compiler_builtins::int::udiv::__udivmoddi4
0.3% 1.9% 782B std core::num::bignum::Big32x40::mul_digits
0.3% 1.9% 768B std core::str::slice_error_fail
0.3% 1.9% 766B std core::fmt::Formatter::pad
0.3% 1.7% 696B std core::fmt::Formatter::write_formatted_parts
0.2% 1.5% 626B std core::num::flt2dec::strategy::dragon::mul_pow10
0.2% 1.5% 610B std core::fmt::Formatter::pad_integral
0.2% 1.5% 604B std core::fmt::num::<impl core::fmt::Debug for usize>::fmt
0.2% 1.2% 466B std core::fmt::write
0.2% 1.1% 434B std core::num::flt2dec::round_up
0.2% 1.0% 414B std <&T as core::fmt::Debug>::fmt
0.2% 1.0% 404B std compiler_builtins::float::add::__addsf3
0.2% 0.9% 384B std compiler_builtins::float::div::__divsf3
0.2% 0.9% 382B std <core::fmt::builders::PadAdapter as core::fmt::Write>::write_str
0.1% 0.9% 358B std compiler_builtins::float::mul::__mulsf3
3.5% 21.7% 8.6KiB And 101 smaller methods. Use -n N to show more.
16.0% 100.0% 39.5KiB .text section size, the file size is 247.3KiB