Application of ARM9 embedded system in excitation regulation device

2.3 ARM and DSP connection
HPI is a parallel serial port, through which ARM can directly access DSP storage space and address mapping storage space of peripheral devices. HPI is mainly composed of address register HPIA, data register HPID, and control register HPIC. ARM first sets the control register and address register, and then reads and writes the data register according to the control signal. Before reading/writing with HPI, the ARM processor must first complete a series of initializations such as its own working mode. The source code is as follows:
SYSCFG=0xeTffe22; /* Turn off the ARM cache */
EXTDBWTH=0K0ffff556; /* Make the external I/O interface work in 32-bit mode */
EXTAC0NO=0x08610000 /* Configure the read and write timing relationship of the external I/O interface */
This code operates on the registers, configures the ARM processor working mode, and then reads and writes the external I/O interface, thereby completing the corresponding operation of the HPI interface. The HPI interface can be used in I/O port mode or I/O access mode. The system platform uses I/O access mode to map the HPI access address register HPIA, data register HPID, and control register HPIC to the space starting at the physical address of memory 0x3fd40000, and operate the HPI through memory access instructions.
The HPI physical address is defined as follows:
#define HPI-Base Ox3fd40000
#define Vpint /* volatile unsigned int */
#define HPICW (Vpint (HPI-Base +0x00))
#define HPICR (Vpint (HPI-Base +0x40)) /* Define HPIC register */
#define HPIAW (Vpint (HPI-Base +0x10))
#define HPIAR (Vpint (HPI-Base +0x50)) /* Define HPIA register */
#define HPIDW (Vpint (HPI-Base +0x20))
#define HPIDR (Vpint (HPI-Base +0x60)) /* Define HPID register */
When communication starts, ARM sends a command to DSP (such as data acquisition), interrupts DSP through the HPI port, and makes DSP enter the corresponding subroutine; at the same time, DSP stores the data in the buffer, and the length of one frame is 256 bytes. When ARM requests data from DSP, it sends a frame synchronization command word to DSP and interrupts DSP at the same time. DSP responds to the interrupt and sends the data to the HPI port RAM. After storing a frame of data, DSP sends an interrupt to ARM. ARM responds to the interrupt, clears the interrupt, takes out the data from the HPI port and stores it in RAM, and sends it to the terminal for display and cyclic refresh. Part of the ARM program flow chart is shown in the figure below:

Figure 3 ARM partial program flow chart

HPI read and write data part of the code:
for (i=0; i
{
HPICW=0x00000000; /*Initialize the control register of the HPI port*/
HPIAW=0x800000000; /*Initialize the address register of the HPI port*/
hpiBaseAddr[i]=HPIDR; /*Read data through HPI and send it to the array for temporary storage*/
CpLen=HPISize;
if (copy_to user (buffer, (_u8*)(&hpi>HpiBaseAddr[j]), CpLen)) return-EFAULT;
/*Copy the data to the user buffer*/
return CpLen
}
In the development of the control unit with DSP as the core, most of the code is written in C language, and the development environment CCS IDE (Code Composer Studio Integrated Development Environment) provided by Ti is used to compile, assemble and link the program, and simulate and debug the program. Finally, the generated DSP executable code is downloaded to the DSP's Flash.

3. Conclusion and innovation
Taking advantage of the powerful functions of ARM9 CPU and the convenient and efficient underlying support provided by embedded Linux multi-process and multi-threaded programming, the excitation regulation device developed has many advantages such as high reliability and easy operation, and plays a pivotal and core role in the excitation regulation control system. This paper introduces the dual-core embedded hardware platform composed of ARM and DSP dual CPUs, gives the overall hardware design diagram of the system, and introduces the design of the ARM and DSP communication parts in detail. In the future, there will be more and more systems based on DSP for data processing and ARM for management, and the application of the two will become more and more extensive.
Innovation: (1) The system uses ARM processor instead of single-chip microcomputer, which greatly improves the system performance; (2) The use of ARM and DSP dual-core embedded system gives full play to the respective advantages of ARM and DSP; (3) The industrial-grade large LCD touch screen replaces the traditional LCD, and the friendly human-machine interface is easy to learn and use.