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Accurate Time Keeping in Embedded Systems

In many embedded systems, there is a need to keep accurate time/date. This is often performed using an RTC (Real-Time Clock). However,  uncalibrated RTC are not that accurate. For example, ST Microelectronics M41T94 RTC datasheet explains that: Uncalibrated clock accuracy will not exceed ±35 ppm (parts per million) oscillator frequency error at 25°C, which equates to about ±1.53 minutes per month. . In order to improve the accuracy, you’ll need to calibrate the crystal for each board at the factory using a frequency counter, that will greatly improve accuracy, for M41T94: When the Calibration circuit is properly employed, accuracy improves to better than ±2 ppm at 25°C. However, calibrating the crystal will further increase the manufacturing costs. Another way to have a very accurate time keeping, is to use the power supply frequency (50 Hz/60 Hz) which is extremely accurate due to interoperability requirements between electricity providers. In the diagram […]

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Socket Programming: Client crashes when exiting server

One of our digital signage applications was crashing when the control server was shutdown at the same time a command was sent with no apparent reason. It would always crash inside the write function (see code below) and no error message were returned. sent = write(fd, buf, n); After a while, we found that in case the connection with the server is lost, and write tries to access the server, it will generate a SIGPIPE signal and in most systems, the application would just exit by default. A simple way to handle this case was to ignore the pipe signal by adding the following line during initialization: signal(SIGPIPE, SIG_IGN); In case the server is down at the time the write function is called, the signal SIGPIPE would be ignored, write would return -1 and errno should return 32 (Broken pipe). Alternatively, if needs be you could also handle the SIGPIPE […]

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Finding a device IP Address

If you are developing software for an Ethernet (or Wifi) device, you’ll need to access the board for debugging and/or testing purpose. If your board does not have user interface or the serial port is not available, you’ll have to find the IP address (assuming it is using DHCP) before accessing the board thru telnet or ssh. A simple way to do that is to ping the broadcast address and check the arp table. > ping -b 192.168.0.255 WARNING: pinging broadcast address PING 192.168.0.255 (192.168.0.255) 56(84) bytes of data. 64 bytes from 192.168.0.246: icmp_seq=0 ttl=64 time=0.018 ms 64 bytes from 192.168.0.101: icmp_seq=0 ttl=64 time=0.217 ms (DUP!) 64 bytes from 192.168.0.246: icmp_seq=1 ttl=64 time=0.023 ms > arp -i eth0 arp -i eth1 Address                  HWtype  HWaddress           Flags Mask            Iface 192.168.0.103            ether   00:50:FC:00:00:01   C                     eth1 192.168.0.109            ether   00:13:20:01:01:01   C                     eth1 If you cannot find your device, it may be configured to […]

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Archos 70 Internet Tablet Video Review

Archos as just released a new 7″ Android Tablet. This device costs around 275 USD (249 Euros), which is a pretty good price for a device based on an ARM Cortex A8 at 1 GHz running Android 2.2, a capacitive touch screen (800×480), HDMI output (Up to 720p), built-in wifi (802.11n) and bluetooth 2.1 as well as a front facing camera. Bear in mind that you won’t be able to take pictures or videos with this device since there is no camera on the back of the device. Go to Archos website to get the full technical specs of Archos 70. Here are two videos of the device by Charbax. The first video shows web browser, video playback, google app market place, video playback on TV thru HDMI and facebook. The second video shows the dolphin web browser used with a bluetooth keyboard, video chat with fring (still have some […]

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D-link Boxee Box available for pre-order

D-link Boxee set-top-box is available for  pre-order on amazon for 199 USD. It can only be pre-ordered to addresses in the US for now and shipments should start in November. D-Link disclosed that its device is based on an Intel Atom processor CE4100 (Sodaville), not an ARM or MIPS processor as many other STBs do. It is running on embedded Linux. Key features listed by D-Link for the device (beside its weird shape) are basically those of the Boxee media-streaming software on which it’s based: Enjoy thousands of shows available for free from your favorite networks, ready to watch at any time Check-out free movies from the web & watch new releases in stunning HD from premium movie services Play videos, songs, or pictures from your computer or home network Plays any non-DRM video, music, and photos and media from anywhere on the Internet The device features the following input/output and […]

Rockchip RK3568/RK3588 and Intel x86 SBCs
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ViewSonic Android Tablet: ViewPad 7

Lots of Android Tablet were shown at IFA 2010 in Berlin. The most hyped was Samsung Galaxy Tab. Charbax has lot of videos about different devices. Among them, ViewSonic Viewpad 7 seems to be worth looking at with Android 2.2, #G, Wifi, video calling, capacitive touch screen and a retail price that should be 399 Euros. It actually seems to be doing all what the pricey Samsung tablet is doing (except lower camcorder resolution). On the hardware side, it is most likely using Qualcomm MSM7227 (ARM11).

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Samsung Galaxy Tab Video

As blogged previously, Samsung released its Android Tablet at IFA in Berlin today. Here’s a video to show off the Samsung Galaxy Tab including the TV commercial at the end: That looks really good until you look at the price tag: 799 Euros. Here are the full specs of this Android tablet: Network: 2.5G (GSM/ GPRS/ EDGE) : 850 / 900 / 1800 / 1900 MHz 3G (HSUPA 5.76Mbps, HSDPA 7.2Mbps) : 900 / 1900 / 2100 MHz OS: Android 2.2 (Froyo) Display: 7.0 inch TFT-LCD, WSVGA (1024 x 600) Processor: Cortex A8 1.0GHz (ARM) Application Processor with PowerVR SGX540 Camera: 3 MP Camera with Auto-Focus and LED Flash 1.3MP front camera for Video Telephony Mini-HDMI connector with 1080p video output. Docking Station GPS (A-GPS) Value-added Features: Android Market™ and Samsung Apps for more applications and contents Readers Hub, Media Hub, Music Hub, Social Hub (Facebook/Google/Outlook) Adobe Flash 10.1 player […]

Boardcon Rockchip and Allwinner SoM and SBC products