Application of ColdFire MCU on Clinux

Introduction to ColdFire Series Processors

Freescale's 32-bit processors are divided into PowerPC series, ColdFire series and DragonBall series. ColdFire series is one of the important components, which can be applied to industrial control, instrumentation, civil products, network products and other fields. ColdFire series has a good cost performance, and its price ranges from US$2 to US$20. ColdFire series processors have many development tools and provide users with some ready-made solutions, which enables users to quickly develop their own application products.

ColdFire processors are divided into V2 core and V4 core. The 52 series is V2 core architecture, and the 54 series is V4 architecture. The following takes the V2 core as an example to introduce its performance:

The V2 core has a variable-length RISC instruction set; has 2 independent pipelines; uses 3-longword FIFO buffers to separate the pipelines from each other; a 32-bit internal address bus supports 4GB of linear address space; a 32-bit data bus; 16 user-available 32-bit general-purpose registers; it supports optimization of high-level language structures and many other features.

The MCF527X series mainly includes MCF5270 to MCF5275 processors, which are mainly suitable for remote monitoring, data security encryption equipment, Ethernet hubs, home routers and other products. Its main features are: V2 ColdFire core, with a processing power of 159MIPS at a clock frequency of 166MHz; 32 32-bit enhanced multiplication and accumulation unit and hardware divider; 8KB or 16KB bytes of configurable instruction/data cache; rich peripheral interfaces; packaging forms include 196-pin BGA and 256-pin BGA packaging.

The MCF523X series products mainly include MCF5232, MCF5235, etc. Its biggest feature is the addition of an enhanced timing processing unit (eTPU). This function is particularly suitable for products with network communication security. It is also its V2 ColdFire core structure.

The main feature of the MCF547X series and MCF548X series products is the use of the fourth-generation enhanced ColdFire core (V4e). They are particularly suitable for tool automation, process control, robotics, medical instruments, etc.

In addition to the above processors, Freescale ColdFire series also includes the earliest used MCF5272 processor, the MCF5282 processor with integrated Ethernet media access controller (MAC) and network application software, and the MCF5249 processor with integrated peripherals and enhanced multiplier and accumulator.

CLinux Application Development

There are two main ColdFire programming environments currently in use. The following takes the MCF5249 development board as an example to introduce the operation and application of CLinux.

CLinux Application Development

1. Establish a host development environment

During development, cross-compilation, assembly and linking tools are used on the host machine to generate executable binary code, and then the executable file is downloaded to the target machine for execution.

The hardware development environment of CLinux mainly consists of a host machine and a target board. It is recommended to install RedHat 9.0 on the host machine, and the target board can be MCF5249, 5282, 5272, etc. The connection between the host machine and the target board can be a parallel cable, a serial cable, or a direct network cable.

2. Development Mode

First, after debugging on the host machine (PC), port it to the target board. In this way, the gdb debugging tool can be used. Porting mainly involves function library issues and modifying Makefile to adapt to different target boards. Usually, the mode of developing directly on the target board is adopted. Connect the host machine and the target board through a serial port line, run minicom on the host machine as the display terminal of the target board, mount the host machine hard disk, and debug the application directly on the target board.
There are three ways to debug the application directly on the target board:

(1) Printing serial port. This is the most commonly used debugging method for embedded systems. It is simple, practical and effective.

(2) Use log record files.

(3) gdb debugging. [page]

CLinux Driver Development

CLinux driver development can be divided into three layers from the application development concept level: upper, middle and lower. The lowest layer is hardware, the middle layer is embedded operating system, and the highest layer is application. The hardware layer and embedded operating system are connected by drivers, and the embedded operating system and application are connected by calls.

In Linux, drivers are implemented by device drivers. Linux divides different devices into three categories: character devices, block devices, and network devices. Common character devices include serial ports, monitors, printers, etc.; common block devices include hard disks, disks, CDs, etc.; network devices are generally various network interfaces.

CLinux Application Examples

QSPI data acquisition based on CLinux

The Serial Peripheral Interface (SPI) is a synchronous serial peripheral interface proposed by Freescale, which allows the CPU to communicate and exchange information with various peripheral interface devices in a serial manner. The QSPI module provides a serial peripheral interface with queue transmission performance.

From the QSPI structure, the QSPI module has 7 signal pins, 4 of which are chip select signals. It has 80 bytes of QSPI RAM. Its control logic is connected to the internal bus. The queue control area is connected to the address register. The 4 peripheral chip select signals are used to select which external device communicates with the QSPI. The chip select signal is only used for simple chip selection, but up to 15 ports can be controlled through an external 4-16 decoder.

For 32-bit ColdFire processors, there are three ways to control QSPI (taking MCF5249 as an example), which are:

1. Bare metal mode, that is, no need for CLinux support, directly set the QSPI register of MCF5249.

2. Set the QSPI registers directly in CLinux and control the QSPI operation as a user application.

3. Add the QSPI control program in the form of CLinux driver and provide the QSPI interface for users. Users can set and control the QSPI through the provided interface.
The data acquisition scheme in this article is the third method.

USB data storage based on CLinux

The USB data storage structure based on CLinux is shown in Figure 1, where the MCF5249 development board is used as the USB HOST and the USB flash drive is used as the storage medium, which can realize flexible data storage and movement.

The main modules of USB driver in CLinux are:

To support USB flash drives, you need to set up CLinux as follows: Execute make menuconfig in the CLinux directory to enter the CLinux configuration interface.

MCF5282EVB board bootloader transplantation

There are two Bootloader operation modes.

Boot loading mode: This mode is also called autonomous mode, that is, the bootloader loads the operating system from the ROM on the target machine into the RAM and runs it, and the whole process does not involve the user.
Download mode: In this mode, the bootloader on the target machine will download the image from the host machine through communication means such as serial port connection or network connection. The image downloaded from the host machine is usually saved to the RAM of the target machine first, and then written to the ROM of the target machine.

The main files of the MCF5282EVB board bootloader transplantation are shown in Figure 2. Since the MCF5282 is a Coldfire series microprocessor, it has similarities with other models of Coldfire microprocessors. The read and write methods of the control registers of the chip peripherals are similar to those of the MCF5206; and the chip peripherals are very similar to those of the MCF5272, with QSPI, QAD, and FEC.