I got few questions from our readers about bit-band feature in ARM Cortex microcontrollers. This seems to be so obvious but also may lead to come confusion while using bit-banding. So let’s look at this feature a little bit closer. Why use bit band Simply speaking Bit banding method allows to perform atomic bitwise operations to memory areas. Why use bit banding? The simplest answer is because ARM Cortex doesn’t have something like BIT CSET or BIT CLEAR commands like most of 8-microcontrollers do. So this is somewhat a work around solution. Another question may rise – Why not using read-modify-write method? Again this method is not reliable in some cases. For instance f there is an interrupt during this operation it can cause data corruption. Other situation may occur in embedded OS when different tasks may modify same memory location. So we want a method that allows to set …
There has been several requests among users to explain more about loading programs in to flash memory of STM32 microcontrollers. This of course is a wide topic but lets focus on how to achieve result – flash program in to MCU. Depending on what arsenal is on your desk you can do in several different ways. Let’s try to go through them in practical way.
STM32F103ZET6 board comes with 3.2 inch graphical LCD which features an ILI9320 controller. Equipped LCD is capable of displaying 252144 colors when driven in 18-bit mode. We are gonna drive it in 16-bit mode, so we are limiting it to 65K colors. LCD driver is based on existing code found on internet which was originally developed for STM3210E board. Only minor modifications were needed like assigning right control pins.
In previous example we implemented a simple demo program that reads buttons by constantly checking their status in main program loop. Obviously this isn’t efficient and convenient way to do that. Imagine your program has to do lots of tasks and in between you also need to check button status – mission becomes impossible unless you use interrupts. In this part we briefly introduce to STM32F10x interrupt system and write example code where LEDs and buttons are serviced within interrupts. ARM Cortex-M3 microcontrollers have advanced interrupt system that is pretty easy manageable. All interrupts are controlled inside Nested Vectored Interrupt Controller (NVIC) which is close to Cortex core to ensure low latency and robust performance. Main features of NVIC include: