Development Of Mini Thermal Printer Firmware Based On STM32 Series ARM Cortex-M3 Microcontroller

The ARM Cortex-M3 processor is the industry-leading 32-bit processor for highly deterministic real-time applications, it not only has excellent computing capacity, quick response and excellent stability, but also meet the demand of low power consumption, high performance. The STM32 family of ARM Cortex-M3-based microcontrollers is a high-performance ARM Cortex-M3 core with low-cost, low-power microcontrollers for embedded applications, had been widely used in the embedded fields such as motor drives, simple industrial control, automotive electronics and micro-printers.Thermal printing technology started earlier in USA, Japan and some other developed countries, where thermal printing products are widely used, updates faster, and thermal printing technology is also constantly upgrading. It had widely used in foreign countries, involving many aspects of society, including various POS sales terminals, gas station, water and electricity charges, hotel tourism, postal and so on. Compared to some developed countries, thermal printing technology R & D in our country is not too late, but once the development has been slow. In recent years, micro thermal printer production has developed rapidly in China, with the rapid development of domestic economy and the increasing demand on information printing aspects of each field, thermal printing technology will become more and more mature and the miniature thermal printer products will have broad market prospects in China.Realization of miniature thermal printer products, the firmware is an essential par. The main work of this paper is to develop a firmware on the development board of thermal printer based on the STM32 series microcontroller with the ARM Cortex-M3 core. Firstly, in context of research projects and the current status quo at home and abroad, the paper describes the main issues to be addressed, needs analysis from feasibility, functionality, and other non-functional perspective.The Developed firmware is a program that programmed into the development board Carrying STM32 ARM Cortex-M3 microcontroller, to be called a system. Practicality follow the principle of system design, stability principle, the principle of real-time, scalable principle, the firmware system architecture designed to include three levels of driver layer, system layer and application layer.Layer is responsible for driving the drive underlying hardware implementation. Device driver module system driver layer includes LED light control module, stepper motor control module and print head control module. The driver layer provides a unified interface to enable device-independent system, that the system should not realize the changing in the driver layer.System layer is actually a simple task scheduling system. In order to ensure real-time, system layer using preemptive task scheduling mechanism, namely a high-priority task can always preempt lower-priority tasks. It provides an interface for the application layer, the application layer to create a task (system layer provided), user can call the function interface like sleeping task, pending task, and restoring task to switch tasks, without concern for task switching concrete realization.Application layer is the core part of the firmware, calls the API interface provided by the driver layer and the system layer, to achieve control of the entire printing process. Application layer includes a data receiving module, a parsing module instruction, the instruction execution module, an exception processing module four modules. From Data received, to the command analysis, and then to print execution, control the entire printing process by the application layer is responsible for the application layer, its performance directly affects the stability of the system.The firmware development process also completed the design and implementation of the instruction set and the font programmed subsystem. During the test, considered aspects of the function, abnormal and performance. The results show that this firmware implements all the instructions in the instruction set, basically does not exist abnormal operation and the printing is efficient.The firmware has been in well used for over three months when the paper completed.