Web3 Looming with Promises

Three startups dedicated on web3 and privacy: The KILT for distributed identity, Partisia for combined computation power, and NVM for overlay routing and strong content security.

MQTT over SSL / TLS with the M2Mqtt library and the Mosquitto broker

http://www.embedded101.com/Blogs/PaoloPatierno/entryid/366/mqtt-over-ssl-tls-with-the-m2mqtt-library-and-the-mosquitto-broker

(written on nov 2 2017)

RESTful Revolution – Refactor Embedded Application

RESTfull revolution has taken place on the net and is in more and more small devices.

(written on sep 20 2016)

C++ Multithread and Exception Safe Programming

Two topics from Dr Dobbs:

http://www.drdobbs.com/cpp/volatile-the-multithreaded-programmers-b/184403766

(this was written on oct 15 2014)

Linux Mind Mapping and Project Management Software

Linux Mind Mapping and Project Management Software: Just ran into the article on linux.about.com, it’s kind of interesting.

http://linux.about.com/od/softorther/fl/Mind-Mapping-with-Freemind.htm

And a few project management software projects the article links to: OpenProj, TaskJuggler, Project Open, DeskAway, Wrike, ACE Project …

Fedora on Acer C7 Chromebook

Since installed ChrUbuntu, Fedora has been on my todo list till now … it’s done! Even better, with double the battery run time!

c7fedora - Fedora on Acer C7 Chromebook

Chromebooks are a great budget laptop or netbook when running Linux. Many people prefer Fedora over Ubuntu. So far there has only been the fantastic ChrUbuntu project that allows Acer C7 Chromebook to load a special kernel with a Ubuntu root file system. Its approach can be used to load Fedora 19 too. The steps below in a few scripts automate the Fedora 19 installation process. It loads a pre-installed Fedora LXDE minimal root file system image. After booting into LXDE it’s free to load KDE or GNOME environments and any other normal packages.

View original post 292 more words

Using Newlib in ARM bare metal programs

Really great and very detailed series of artistic work on ARM and emulation.

Posted by Balau on Dec 16 of 2010.

When dealing with embedded software, I often find useful to have the standard C functions we all learn during our first programming course: printf, malloc, getchar, strncpy, …
A common way to have them is using Newlib. Newlib is an implementation of the standard C library that is specifically thought to run somewhere with low resources and undefined hardware. The idea of Newlib is to implement the hardware-independent parts of the standard C library and rely on few low-level system calls that must be implemented with the target hardware in mind.

I compiled Newlib with the CodeSourcery ARM compiler for bare-metal targets: Sourcery G++ Lite 2010.09-51. Once the toolchain is installed, the commands I used to download compile Newlib are:


$ wget ftp://sources.redhat.com/pub/newlib/newlib-1.18.0.tar.gz
$ tar xzf newlib-1.18.0.tar.gz
$ cd newlib-1.18.0/
$ ./configure --target arm-none-eabi --disable-newlib-supplied-syscalls<
$ make
$ cd ..


The “--disable-newlib-supplied-syscalls” option is necessary because otherwise Newlib compiles some pre-defined libraries for ARM that are useful in conjunction with debug features such as the RDI monitor. Many different outputs are compiled inside the arm-none-eabi subdirectory, but in particular the “libc.a” archive in the newlib directory is the one I use.

As an example, I want to compile the following “test.c” program:


#include
#includeextern char *heap_end; /* Defined in syscalls.c */

void c_entry() {
char c;
char *ptr = NULL;
size_t alloc_size = 1;
do {
c =getchar();
printf(“%d: %c\n”, c, c);

ptr = realloc(ptr, alloc_size);
if(ptr == NULL) {
puts(“Out of memory!\nProgram halting.”);
for(;;);
} else {
printf(“new alloc of %d bytes at address 0x%X\n”, alloc_size, (unsigned int)ptr);
alloc_size <<= 1;
printf("Heap end = 0x%X\n", (unsigned int)heap_end);
}
} while (1);
}

The program uses standard input/output functions and allocates more and more memory with realloc, printing some information to understand what’s going on. The idea is to use the UART serial port as the input/output, and monitor how the memory is managed. The heap_end variable is something that I will implement and use later to manage the memory allocation.

The program needs at least some basic starting code “startup.s” that I borrow from a previous example of mine about the hello word bare metal qemu post:


LDR sp, =stack_top
BL c_entry
B .


And the linker script “test.ld” again is a modified version from the hello word bare metal qemu post:


SECTIONS
{
. = 0x10000;
.ro : {
startup.o (.text)
*(.text)
*(.rodata)
}
.rw : {
*(.data)
*(.bss)
*(COMMON)
}
. = ALIGN(8);
heap_low = .; /* for _sbrk */
. = . + 0x10000; /* 64kB of heap memory */
heap_top = .; /* for _sbrk */
. = . + 0x10000; /* 64kB of stack memory */
stack_top = .; /* for startup.s */
}


more

more


and more
more


Freedom Embedded

When dealing with embedded software, I often find useful to have the standard C functions we all learn during our first programming course: printf, malloc, getchar, strncpy, …
A common way to have them is using Newlib. Newlib is an implementation of the standard C library that is specifically thought to run somewhere with low resources and undefined hardware. The idea of Newlib is to implement the hardware-independent parts of the standard C library and rely on few low-level system calls that must be implemented with the target hardware in mind.

I compiled Newlib with the CodeSourcery ARM compiler for bare-metal targets: Sourcery G++ Lite 2010.09-51. Once the toolchain is installed, the commands I used to download compile Newlib are:

The “--disable-newlib-supplied-syscalls” option is necessary because otherwise Newlib compiles some pre-defined libraries for ARM that are useful in conjunction with debug features…

View original post 515 more words

Hello world for bare metal ARM using QEMU

Really great and very detailed series of artistic work on ARM and emulation.

Freedom Embedded

Last time I wrote about writing and debugging bare metal ARM software using the CodeSourcery toolchain. Now I want to exploit QEMU’s emulation of a complete system and create the simplest “Hello world!” example.

The QEMU emulator supports the VersatilePB platform, that contains an ARM926EJ-S core and, among other peripherals, four UART serial ports; the first serial port in particular (UART0) works  as a terminal when using the -nographic or “-serial stdio” qemu option. The memory map of the VersatilePB board is implemented in QEMU in this board-specific C source; from that I note the address where the UART0 is mapped: 0x101f1000. The code that emulates the serial port inside QEMU (here in the source repository) implements a subset of the functionalities of the PL011 Prime Cell UART from ARM; there is a useful technical manual from the ARM info center that describes…

View original post 672 more words

Emulating ARM PL011 serial ports

Really great and very detailed series of artistic work on ARM and emulation.

Freedom Embedded

QEMU is able to emulate ARM systems with multiple serial ports, for example the Versatile PB. It has the ability to direct them to many types of host resources such as standard I/O, a pseudo-terminal or a telnet port. I started from my hello world example for bare-metal ARM programs to control three different serial ports. In the Versatile PB manual there’s a section, called Memory Map, that includes the absolute addresses of the mapped peripherals. For example, the UART 0, 1 and 2 interfaces are placed at addresses 0x101F1000, 0x101F2000 and 0x101F3000 respectively. Inside the manual, the programmer’s model for the UART peripherals indicates the ARM PrimeCell UART (PL011) Technical Reference Manual as reference. In the PL011 manual we can find a detailed description of the UART memory mapped registers. From that decription I implemented a C struct that renders easy to use the serial ports. The complete…

View original post 327 more words

ARM Tiny Linux Emulated in QEMU

Free Electrons has an excellent example of a tiny ARM Linux demo that runs in QEMU. The footprint, including everything, is about 2.1 M. The full text below is for your convenience, be sure to visit the original site.

From this simple example, much more can be achieved.