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STM32F429 Discovery board

December 23, 2013 in Hardware, Microcontroller, STM32 by admin



The new STM32F429 discovery board key features are impressive:

  • STM32F429ZIT6 microcontroller featuring 2 MB of Flash memory, 256 KB of RAM in an LQFP144 package
  • On-board ST-LINK/V2 with selection mode switch to use the kit as a standalone
  • ST-LINK/V2 (with SWD connector for programming and debugging)
  • Board power supply: through the USB bus or from an external 3 V or 5 V supply voltage
  • 2.4″ QVGA TFT LCD
  • SDRAM 64 Mbits
  • L3GD20, ST MEMS motion sensor, 3-axis digital output gyroscope
  • Six LEDs:
    • LD1 (red/green) for USB communication
    • LD2 (red) for 3.3 V power-on
    • Two user LEDs:LD3 (green), LD4 (red)
    • Two USB OTG LEDs:LD5 (green) VBUS and LD6 (red) OC (over-current)
  • Two pushbuttons (user and reset)
  • USB OTG with micro-AB connector
  • Extension header for LQFP144 I/Os for a quick connection to the prototyping board and an easy probing.

Like every Discovery board, it come with a huge amount of samples. It also has the Standard Peripheral Library available to start development with ease and it featuring  an embedded ST-Link/V2 . Read the rest of this entry →

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Cortex-M3 supervisor call (SVC) using GCC

December 12, 2013 in Code Snippets, Microcontroller, Source Code, Tips & Tricks, Tutorial by admin

cortex-m3Origina article here.

The Cortex-M3 has a new assembler instruction SVC to call the supervisor (usually the operating system). The ARM7TDMI used to call this interrupt SWI, but since this interrupt works differently on Cortex-M3, ARM renamed the instruction to make sure people recognize the difference and implement those calls correctly. The machine opcode however is still the same (bits 0-23 are user defined, bits 24-27 are ones).

On the Cortex-M3, other interrupts can interrupt the processor during state saving of the SVC interrupt (late arrival interrupt handling). Those late arriving interrupts most certainly leave the registers corrupted after execution. Therefor we cannot read the parameters form registers r0 to r4 directly as we could on the ARM7TDMI using SWI interrupts. Fortunately, the Cortex-M3 saves all registers used in standard C procedure call specification (ABI) on the stack. So the SVC handler can get the parameters directly from the stack. Read the rest of this entry →

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New lithium/sulfur battery doubles energy density of lithium-ion

December 12, 2013 in News by admin


Batteries. We buy them at the store, use them up, and throw them away without much thought. In reality, however, batteries are remarkably complex electrochemical devices that are continually evolving. The latest example of this comes from the Lawrence Berkeley National Laboratory, where researchers have invented an advanced lithium/sulfur (Li/S) cell that offers a unique combination of energy storage, power, recharge speed, and survivability.

Lithium/sulfur rechargeable batteries offer a remarkably large capacity for energy storage, mainly because two electrons are produced each time a molecule is processed through the battery’s chemistry.

A basic Li/S cell consists of a lithium anode, a carbon-sulfur cathode, and an electrolyte that permits lithium ions to pass. The overall cell reaction during discharge converts lithium metal in the anode into Li2S at the surface of the cathode. The flow of two lithium ions from the anode to the cathode is then balanced by the flow of two electrons between the battery contacts, delivering double the current of a Li-ion battery at a voltage between about 1.7 and 2.5 volts, depending on the state of charge of the cell. Lithium polysulfides are formed at intermediate charge levels, which affect the cell voltage as indicated above.

That’s the good news. The bad news involves a host of materials problems associated with the basic Li/S chemistry and some side reactions. When the sulfur in the cathode absorbs lithium ions from the electrolyte, the Li2S has nearly double the volume of the original sulfur. This is a very large source of mechanical stress on the cathode, which causes mechanical deterioration, reduces the electrical contact between the carbon and the sulfur (the path whereby electrons flow to allow the reaction to occur), and prevents the flow of lithium ions to the sulfur surface.

Another problem is that lithium and sulfur generally don’t react immediately to form Li2S, but rather get there through a series of intermediate species, such as Li2S8, Li2S6, etc. Sulfur itself and Li2S are essentially insoluble in the typical electrolyte used in Li/S cells, but these intermediate “polysulfides” often are soluble, which causes an ongoing and severe loss of sulfur at the cathode. Other problems appear, such as a roughening of the lithium anode surface with large charge or discharge currents. All of these problems result in a basic Li/S cell being a very bad battery.

The Li/S battery chemistry, however, offers the potential for such wonderful battery performance that, since its discovery in the 1960s, a lot of work has been aimed at solving these problems. Engineers and scientists have tried putting the sulfur inside nanochannels as well as using lithium-silicon-carbon alloy anodes, sulfur polymer cathodes, and a host of other imaginative attempts at solving the interlocked Li/S battery performance limitations. While a good deal of progress has been made, development of a practical Li/S cell has eluded researchers for half a century.

The Lawrence Berkeley team addressed these problems by developing a nanocomposite cathode that addresses the three main problems presented by Li/S cells. The new cathode material is a sulfur-graphene oxide nanocomposite held together using an elastic polymer binder.

For the entire article, follow this link.

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Motorola’s prototype modular phone is almost ready

December 8, 2013 in News by admin

phonebloks_large_verge_medium_landscapeAccording to a Youtube interview, the Motorola’s prototype modular phone is almost in prototype stage. Motorola is partnering with 3D Systems in an attempt to make the idea a reality and take phone customization beyond cases and colors.





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Google announces data export feature for Gmail, Google Calendar data

December 8, 2013 in News by admin

JESS3_Gmail_Makingof-11via ArsTechnica:

“Gmail and Google Calendar users interested in obtaining a copy of all of their messages and appointments will soon have a much easier way to do so: Google today introduced the ability to download data from those services from your account settings page. Google Calendar users will be able to download their data starting today, while Gmail support “will be rolled out over the next month.”

The data is exported in standard, widely supported formats—MBOX for e-mail and iCalendar for your appointments. Most e-mail clients and services can read these files, making it easier to switch from Gmail and Google Calendar to a competing service or even an e-mail server you run yourself (for the privacy-minded among you). You can download individual e-mail labels or calendars or opt to download everything at once. Your data will remain stored on Google’s servers unless you delete it or close your account, however.

For the entire article, please follow this link.

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