embedded

问题 Using a microcontroller (PIC18F4580), I need to collect data and send it to an SD card for later analysis. The data it collects will have values between 0 and 1023, or 0x0 and 0x3FF. So what I need to do is convert 1023 into a base 10 string of literal ASCII values (0x31, 0x30, 0x32, 0x33, ...). My problem is that the only way I can think of to split the digits apart requires a lot of division. char temp[4]; temp[0] = 1023 % 10; temp[1] = (1023 % 100) / 10; temp[2] = (1023 % 1000) / 100; temp

问题 I am calculating angles from a 3-axis accelerometer, but my compiler doesn't have a atan or atan2 function. It has a reserved memory slot, but it calls a function i can't find in any files. My compiler is Keil µVision 4 running the ARMCC compiler. The compiles has the file math.h, but the function is extern and doesn't exist: extern _ARMABI double atan2(double /*y*/, double /*x*/); Is there a lib or function I can include that has the function arctan implemented? Or is there an alternative

问题 I am calculating angles from a 3-axis accelerometer, but my compiler doesn't have a atan or atan2 function. It has a reserved memory slot, but it calls a function i can't find in any files. My compiler is Keil µVision 4 running the ARMCC compiler. The compiles has the file math.h, but the function is extern and doesn't exist: extern _ARMABI double atan2(double /*y*/, double /*x*/); Is there a lib or function I can include that has the function arctan implemented? Or is there an alternative

问题 [This question is similar to this one, but I am also interested in the possibility of a sandbox.] I am considering embedding a scripting language in my C#/.NET application and then exposing some of my application's API to the scripts. There seem to be multiple good options for this (Lua, Boo, IronPython, etc.), but are there easy options for restricting the scripting language's built-in functions from being used? For example, I do not want the scripts to be able to perform I/O except through

问题 Currently, I am learning some FPGA design techniques using VHDL, my problem is whether we can use := and <= interchangeably in VHDL or not, though I've seen the use of := in constants declarations and <= in assignments? Thanks in advance! 回答1: The rules are a little more complex than this, but basically: you use <= to do signal assignment, which takes effect on the next delta cycle. You use := to do variable assignment, which takes place immediately. So if you have a signal, you always use <=

问题 I'm new to Yocto Project. The initial idea is to create a custom image based on core-image-full-cmdline (this is with no windowing system) and generate a Qt5 SDK against this image. So my target to be able to run Qt applications needs to have some headers & libraries installed, isn't ? What I must specify on my image recipe ? Doing $ bitbake my_image -c populate_sdk will generate my_image with Qt5 support + SDK installer ? As I understood, to get a Qt SDK the steps would be: Download and add

问题 I am running Linux kernel 3.3 on Xilinx's Microblaze with full MMU. the task that I am doing requires me to know the following: I need to create a text file (buffer) and locate the physical address of this buffer and I don't want the kernel to write this file into discontinuous regions of memory. the reason I need this because I have a DMA engine that streams data from a preset physical memory address, so I need to force Linux to create the buffer file at that exact memory location, so that

问题 Microcontrollers often require a register to be read to clear certain status conditions. Is there a portable way in C to ensure that a read is not optimized away if the data is not used? Is it sufficient that the pointer to the memory mapped register is declared as volatile? In other words, would the following always work on standard compliant compilers? void func(void) { volatile unsigned int *REGISTER = (volatile unsigned int *) 0x12345678; *REGISTER; } I understand that dealing with

问题 Microcontrollers often require a register to be read to clear certain status conditions. Is there a portable way in C to ensure that a read is not optimized away if the data is not used? Is it sufficient that the pointer to the memory mapped register is declared as volatile? In other words, would the following always work on standard compliant compilers? void func(void) { volatile unsigned int *REGISTER = (volatile unsigned int *) 0x12345678; *REGISTER; } I understand that dealing with

问题 I am looking for an efficient algorithm in C to bitwise-transpose 8 bytes of data. What I mean with this is that if I have 8 bytes like this: 00011100 00111000 00000001 00000000 11000000 00000000 11111111 01010101 I want to get the following 8 bytes: 00001010 00001011 01000010 11000011 11000010 10000011 00000010 00100011 And since I want to use this on an embedded platform, it should be as fast as possible :-) All ideas are much appreciated! 回答1: See Hacker's Delight, Chapter 7-3. 来源： https:/