arm

iPhone/iPad double precision math

由 ╄→гoц情女王★ 提交于 2020-01-14 07:44:27
问题 The accepted answer to this Community Wiki question: What are best practices that you use when writing Objective-C and Cocoa? says that iPhones can't do double precision math (or rather, they can, but only emulated in software.) Unfortunately the 2009 link it provides as a reference: Double vs float on the iPhone directly contradicts that statement. Both of these are old, being written when the 3GS was just coming out. So what's the story with the latest arm7 architecture? Do I need to worry

stack traces stop at the leaf register (lr)

由 白昼怎懂夜的黑 提交于 2020-01-14 05:14:25
问题 Often I see ARM stack traces (read: Android NDK stack traces) that terminate with an lr pointer, like so: #00 pc 001c6c20 /data/data/com.audia.dev.qt/lib/libQtGui.so #01 lr 80a356cc /data/data/com.audia.dev.rta/lib/librta.so I know that lr stands for link register on ARM and other architectures, and that it's a quick way to store a return address, but I don't understand why it always seems to store a useless address. In this example, 80a356cc cannot be mapped to any code using addr2line or

Cross Compile zlib for ARM

由 余生长醉 提交于 2020-01-14 04:15:48
问题 I try cross compile zlib for arm-poky-linux-gnueabi but I've an error when I launch make : ...:~/zlib-1.2.11$ AR=$HOST-ar CC=$HOST-gcc RANLIB=$HOST-ranlib ./configure --prefix=$HOME/zlibARM Checking for shared library support... Building shared library libz.so.1.2.11 with arm-poky-linux-gnueabi-gcc. Checking for size_t... Yes. Checking for off64_t... Yes. Checking for fseeko... Yes. Checking for strerror... Yes. Checking for unistd.h... Yes. Checking for stdarg.h... Yes. Checking whether to

DSP libraries - RFFT - strange results

由 自闭症网瘾萝莉.ら 提交于 2020-01-13 20:23:30
问题 Recently I've been trying to do FFT calculations on my STM32F4-Discovery evaluation board then send it to PC. I have looked into my problem - I think that I'm doing something wrong with FFT functions provided by manufacturer. I'm using CMSIS-DSP libraries. For now I've have been generating samples with code (if that works correct I'll do sampling by microphone). I'm using arm_rfft_fast_f32 as my data are going to be floats in the future, but results I get in my output array are insane (I

Relocate the ARM exception vectors?

由 倾然丶 夕夏残阳落幕 提交于 2020-01-13 20:19:07
问题 How would I relocate the ARM exception vectors ? Basically, I need to be able to remap them in a way, so when the ARM core tries to execute the vector, it should execute the custom exception vector that is stored in kernel's RAM bit and not in the ROM that is at 0x0 . Is that possible? Or am I meant to route the interrupts to the kernel from the ROM ? So essentially, is there a way of telling the ARM core, " here is the new address for your vector table "? I know that you can start the CPU in

Libraries compatibilty by cross-compiling node for armv5

由 被刻印的时光 ゝ 提交于 2020-01-13 13:52:35
问题 I try to cross-compile node for my QNAP armv5te machine, on my Ubuntu 14.04 Desktop x64. A node QPKG exists in QNAP App-center, but its version is old (0.8.22). Here are informations about the server : Linux SERVERNAME 3.4.6 #1 Mon Dec 29 06:00:47 CST 2014 armv5tel unknown Processor name : Feroceon 88F6281 rev 1 (v5l) @ 1.2 GHz BogoMIPS : 1196.85 Features : swp half thumb fastmult edsp CPU implementer : 0x56 CPU architecture : 5TE CPU variant : 0x2 CPU part : 0x131 CPU revision : 1 Hardware :

How to use QEMU for learning ARM Linux kernel development?

由 送分小仙女□ 提交于 2020-01-13 11:10:10
问题 I want to learn it like developing some device driver etc and use QEMU for this because i have no hardware board for ARM like beagle board. What you guys suggest? Can i use Qemu simulator to learn Linux kernel on ARM targets? or any other option i should try ? 回答1: It depends on what you want to learn: hardware or software. If you really want to experiment with the different GPIO output to implement things like servo motor control, LED light blinking and display, a cheap board (eg, Raspberry

micropython compiling with arm-none-eadi- in cygwin

由 六月ゝ 毕业季﹏ 提交于 2020-01-13 09:48:59
1. Download & Decompression 1.1 download micropython path: http://micropython.org/download/ Note: 使用公司的网络git没有安全认证，没有搞定网络，索性就直接下载完整包，本地解压 ~/micropython $ git clone https://github.com/micropython/micropython Cloning into 'micropython'... remote: Enumerating objects: 75723, done. remote: Total 75723 (delta 0), reused 0 (delta 0), pack-reused 75723 Receiving objects: 100% (75723/75723), 41.91 MiB | 18.00 KiB/s, done. Resolving deltas: 100% (54847/54847), done. Checking out files: 100% (3427/3427), done. 1.2 download gcc-arm-none-eadi compiler Path: https://developer.arm.com/tools-and-software

Coherently understand the software-hardware interaction with regard to DMA and buses

由 百般思念 提交于 2020-01-13 06:37:06
问题 I've gathered some level of knowledge on several components (including software and hardware) which are involved in general DMA transactions in ARM based boards, but I don't understand how is it all perfectly integrated, I didn't find a full coherent description about this. I'll write down the high level of the knowledge I already have and I hope that someone could fix me where I'm wrong and complete the missing parts so the whole picture would be clear. My description starts with the

Compute clock cycle count on ARM Cortex-a8 BeagleBone Black

由 巧了我就是萌 提交于 2020-01-13 06:11:46
问题 I want to compute the clock cycle count for a specific function inside my c code which is going to be compiled and run on BeagleBone Black. I have no idea how I can do this. I searched over the web and I found this instruction: Clock Read method on Arndale board: Step-1: Inserting kernel module to enable user space access to PMU counters. Untar the attached file “arndale_clockread.tar.bz2” which is having Makefile and enableccnt.c. In Makefile change the “KERNELDIR” with your kernel source
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