STM32L151 makefile project

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 …

Reading OBD2 data without ELM327, part 2 – K-Line

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 …

Reading OBD2 data without ELM327, part 1 - CAN

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 …

FreeRTOS on Kinetis E Cortex M0+ : easy porting tutorial

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 …

XMEGA power down mode for battery powered devices

This post describes how to implement firmware-controlled device power switching on an XMEGA. I am working on a portable device that is powered from a Li-Ion cell, has an USB socket for charging, MCU, couple of LEDs and a button. I wanted to keep the design as simple as possible …

Kinetis - relocating variables to upper SRAM

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 …

Practical NodeMCU endurance with a big NiCd battery pack

Some time ago I have built a WiFi thermometer with a NodeMCU and a 6Ah recycled nickel-cadmium battery. WiFi is probably the least power-efficient communication methods but I was curious how long could a NodeMCU run from a big battery pack.

It took some time to get meaningful data...

After …

XMEGA USART driver with TX DMA

This is a quite universal, non-blocking UART driver for XMEGA. It supports both transmission (with optional DMA) and reception. Receive side can deliver callbacks whenever a complete line (terminated with \n) is received or received bytes can be retrieved one-by-one from a ringbuffer (more useful for GPS units). This driver …

XMEGA high-performance SPI with DMA

I developed an universal SPI driver for XMEGA line of MCU for a battery powered device where power efficiency was important. To get anything started on new hardware I have started with a simpler code first which uses interrupts and then I began looking at using XMEGA's DMA controller (that …

XMEGA and HD44780 LCD

Character LCD are one of the easiest and cheapest way of adding output to a microcontroller system. The world of character LCDs has mainly standarized on HD44780 controller chip, which was designed to be interfaced with the rest of the system by a parallel bus but today simple bit-banging does …