I have published a basic Makefile project for STM32L151 on Github. I plan to develop it into a low-power wireless sensor network using SP1ML modules. The modules contains STM32L151RB MCU with 128K of flash, SPIRIT1 transceiver chip, antenna and passive components. Basically everything needed to make an 868MHz radio network.
Continue reading “STM32L151 makefile project”
K-Line is another popular OBD2 interfacing standard, that has been used in European cars before CAN bus became common. There are a couple of physical variations (K-line, K+L, KKL) and slightly different protocols (KWP2000 or Keyword Protocol, and ISO 9141) running on those lines. Basically all you need to talk to an older car is an MCU with a UART and a single transistor. 🙂
Continue reading “Reading OBD2 data without ELM327, part 2 – K-Line”
All modern cars have an OBD2 diagnostic connector that allows reading many engine and drivetrain parameters like RPM, vehicle speed, temperatures etc.
Most of car interfaces use a special protocol translating chip like ELM327 or STN1110 to convert different vehicle protocols (that depend on the age and brand of the car) into an easier to use serial protocol with AT-commands.
I wanted to build a datalogger that would fit into a OBD2 connector. There was no space to fit my microcontroller and another chip to do protocol conversion, so I investigated and reverse-engineered the most common OBD2 protocols to be able to implement them directly on my MCU.
Continue reading “Reading OBD2 data without ELM327, part 1 – CAN”
FreeRTOS is a popular, open-source operating system that can run on a variety of microcontrollers. This post shows how to make a minimal working setup with two tasks on a new MCU without starting from a complete demo code or code generators (like Processor Expert) on an inexpensive development board FRDM-KE06Z from NXP. All examples use static memory allocation. Most of the procedures and tips mentioned here apply equally well to all Cortex-M microcontrollers.
Continue reading “FreeRTOS on Kinetis E Cortex M0+ : easy porting tutorial”
NXP Kinetis microcontrollers have an inconvenient architectural feature – split RAM. The memory is split into two areas of equal size. You can run into this issue when the size of all RAM variables (data+bss) approaches half size of available SRAM. It manifests itself with a linker error looking similar to this:
ld: region `m_data' overflowed by 132 bytes
I will use an MK22FN512 as an example, but this post applies equally to all Kinetis K-series MCUs.
Continue reading “Kinetis – relocating variables to upper SRAM”