基于ARM7的GPRS程序代码

embed ===== This example illustrates a simple C program, suitable for embedded applications. The main C program is contained in main.c. This has a main() function, which calls subroutines to show the use of printf(), sprintf(), floating point printf() and malloc(). This can be compiled/linked on its own and executed in the semihosting environment (see build a below). Alternatively, the project can be built as an embedded application with no semihosting (builds b & c). This example can be built in three different ways, in increasing order of complexity: a. Non-embedded (semihosted), scatterloaded b. Embedded, with ROM fixed at 0x0, scatterloaded c. Embedded, ROM/RAM remapped, scatterloaded For options b and c, all hard coded addresses are located in the scatterfile To build the example, either: - use the supplied batch files (build_a.bat, build_b.bat, build_c.bat), or - use the supplied CodeWarrior project file (embed.mcp, with 3 targets: Semihosted, EmbeddedScatter, EmbeddedScatterRemap), or - create your own make files. These create an ELF image (embed.axf) suitable for loading into an ARM debugger. A Motorola32 ROM image (embed.m32) is also created, suitable for loading into a target, for example, downloading into the flash memory of an ARM Integrator board. To convert it into an embeddable application, additional files are provided: 1. vectors.s contains exception vectors and exception handlers. Where there is ROM fixed at 0x0 (build_b), these are hard-coded at 0x0. Where ROM/RAM remapping occurs (build_c), these are copied from ROM to RAM. 2. init.s performs ROM/RAM remapping (if required), initializes stack pointers and interrupts for each mode, and finally branches to __main in the C library (which eventually calls main()). 3. retarget.c implements a 'retarget' layer for low-level I/O. Typically, this would contain your own target-dependent implementations of fputc(), ferror(), etc. This example provides implementations of fputc(), ferror(), _sys_exit(), _ttywrch() and __user_initial_stackheap(). Here, semihosting SWIs are used to display text onto the console of the host debugger. This mechanism is portable across ARMulator, Angel and Multi-ICE. Alternatively, to output characters from the serial port of an ARM Integrator Board (see serial.c), use '#define USE_SERIAL_PORT' or compile with '-DUSE_SERIAL_PORT'. 4. serial.c implements a simple (polled) RS232 serial driver for the ARM Integrator Board. It outputs single characters on Serial Port A at 38400 Baud, 8 bit, no parity, 1 stop bit. To monitor the characters output, use a null-modem cable to connect Serial Port A to an RS232 terminal or PC running a terminal emulator, e.g. HyperTerminal. 5. In addition the files stack.s and heap.s are used to create dummy variables which are placed in memory by the scatter load file. These can then be used to place the stack and heap respectively. 6. Finally uart.c instantiates a struction corresponding to the layout of the uart registers. This structure is located in memory by the scatter load file. To ensure that no functions which use semihosting SWIs are linked in from the C library, __use_no_semihosting_swi is used for the 2 'embeddable' builds. The 3 different builds can be executed either on the ARMulator, or on real hardware (e.g. Integrator board via Multi-ICE). To run the examples on real hardware, please note: i. For Semihosted (build_a) build targets, set $top_of_memory to a suitable value via the debugger. The (unexpanded) Integrator CM has 256KB of SSRAM fitted, so set $top_of_memory=0x40000. If additional SDRAM is fitted, set $top_of_memory appropriately. It is not necessary to set $top_of_memory for the other builds, because they implement __user_initial_stackheap(). ii. For EmbeddedScatter (build_b.bat) and EmbeddedScatterRemap (build_c.bat) build targets, set $vector_catch=0 to prevent exceptions being caught, and to free up a watchpoint unit in the EmbeddedICE Logic. iii. EmbeddedScatterRemap (build_c.bat) is intended to be downloaded into Flash (see below). Building for Thumb ------------------ The supplied batch files (build_a.bat, build_b.bat, build_c.bat) and supplied CodeWarrior project files build ARM-only versions of this code. To build ARM/Thumb interworking versions of this example, where the bulk of the C code is compiled for Thumb, change the invocations of 'armcc' into 'tcc -apcs /interwork', so that e.g. build_c.bat becomes: armasm -g vectors.s armasm -g -PD "ROM_RAM_REMAP SETL {TRUE}" init.s armasm -g stack.s armasm -g heap.s REM Use the following two lines to build without using the serial port. tcc -apcs /interwork -c -g -O1 main.c -DEMBEDDED -DROM_RAM_REMAP tcc -apcs /interwork -c -g -O1 retarget.c REM Use the following two lines to build using the serial port. REM tcc -apcs /interwork -c -g -O1 main.c -DEMBEDDED -DROM_RAM_REMAP -DUSE_SERIAL_PORT REM tcc -apcs /interwork -c -g -O1 retarget.c -DUSE_SERIAL_PORT tcc -apcs /interwork -c -g -O1 uart.c -I..\include tcc -apcs /interwork -c -g -O1 serial.c -I..\include armlink vectors.o init.o main.o retarget.o uart.o serial.o stack.o heap.o -scatter scat_c.scf -o embed.axf -entry 0x24000000 -info totals -info unused fromelf embed.axf -bin -o embed.bin fromelf embed.axf -m32 -o embed.m32 Downloading to Flash -------------------- Follow the instrictions below to download the 'Embedded, scatterloaded' examples 'build_b' and 'build_c' to the flash memory of an ARM Integrator board, so that you can execute/debug the image at source level. Use the debugger's File->Flash-download feature, which uses flash.li/.bi. This requires a plain binary image to be built with: fromelf embed.axf -bin -o embed.bin See 'AXD and armsd Debuggers Guide', Appendix D, "Using the Flash Downloader". Alternatively: Follow the steps 1-8 below to download using the Integrator's Boot Loader: These steps require a terminal emulator such as 'HyperTerminal'. 1. Connect the Integrator board to the host computer using a null modem serial cable. 2. Invoke the terminal emulator and ensure it has the following settings: - Baud rate 38400 - Data bits 8 - No parity - Stop bits 1 - Flow control Xon/Xoff 3. Ensure switches 1 and 4 on the Integrator board are in the 'ON' position and reset the board. 4. Enter 'l' to load flash image at the Boot Loader prompt in the terminal window. 5. Transfer the 'embed.m32' file via the serial cable using the terminal tools. In Hyperterminal this is done by selecting 'Transfer->Send Text File' from the menu and navigating to the embed.m32 file. 6. Once the image has loaded (approx 25 seconds) terminate the flash transfer by pressing Ctrl-C. 7. Ensure switch 1 is returned to the 'OFF' position. 8. The image is now present in flash and will be executed when the board is reset. Output from the image will be sent to the terminal window only if the image was built using the -USE_SERIAL_PORT option. Otherwise output must be viewed using AXD with the image debug symbols via a connection to the board such as Multi-Ice. Memory Maps ----------- The following diagrams illustrate the Memory Maps for this example, for each different build: build_a.bat: 0x08000000 (ARMulator) or +----------+ 0x00040000 (Integrator board) | stack | | VV | ~ ~ | ^^ | | heap | +----------+ Image$$ZI$$Limit | ZI data | +----------+ | RW data | +----------+ | | | | | program | | (RO+RW) | | | | | +----------+ 0x8000 build_b.bat --- +----------+ 0x280800