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Showing content with the highest reputation on 07/10/18 in all areas

  1. 1 point
    Even though this might be true what's important is the thermal considerations and hence substrate temperature. A large component of overall energy consumption of an FPGA is switching those IOs. Thermal issues cause voltage regulators to fail as well if heat can't be dissipated properly ( since you raise the topic ). There's no on-board temperature sensor for Spartan 3 devices. As a general rule I use an external driver for high current applications; they are certainly cheaper and easier to replace. Having said all of this I suspect that driving a couple of seven segment displays using the minimum IO current won't be a problem for your board. This might not be necessary... but it certainly is a good idea as a prophylactic practice, especially when used in a development/hobby environment and when placed close to the pins or balls using the smallest SMT package that can handle the current. Accidents and static discharge happen. Proper termination is also good practice.
  2. 1 point
    Remember to add current limiting resistors. The drive strength settings for the I/O pins are how much current can be sourced/sunk and still give valid logic voltages. Short circuit currents are much higher - 50mA or higher.
  3. 1 point
    They are very robust. Xilinx is a bit shy in telling numbers, but their posts indicate that they are short circuit proof. https://forums.xilinx.com/t5/Virtex-Family-FPGAs/Effect-of-short-circuit-on-V6-outputs/m-p/227493#M13565 https://www.xilinx.com/support/answers/23277.html I got the impression that reports of failed voltage regulators are more common than busted FPGAs (expect that blowing one pin kills the whole IO bank).
  4. 1 point
    @Adriann, As I recall the minimum source/sink current for the Spartan 3 is 12ma ( it might be 6 ma ). But it it up to you to get the datasheet, look in the DC characteristics and verify this. Always take this advice even if someone offers and answer. As to how much current you can safely drive on multiple outputs the answer is more complicated. It depends on a lot of things like which bank they are on, how many IOs are switching simultaneously, how well the FPGA is connected to a thermal sink, etc. Again, whether or not you want to set the IO to maximum current requires some knowledge of the specification for your part and analysis.
  5. 1 point
    Piotr Rzeszut

    Analog Discovery 2 vs NI myDAQ

    Hi, NI myDAQ has an input sample rate of 200 kSPS and bandwidth of 400kHz, where AD2 has 100MSPS and 30MHz+ (with adapter) => point for AD2 NI myDAQ has maximum input voltage +-10V, where AD2 has +-25V => point for AD2 NI myDAQ has an output sample rate of 200 kSPS, where AD2 has 100MSPS => point for AD2 NI myDAQ has maximum output voltage of +-10V, where AD2 has +-5V => point for NI myDAQ NI myDAQ has a built-in multimeter (so it is able to measure in addition to voltage, also resistance, current, diode voltage without any additional adapters) AD2 requires separate adapters for such measurements => point for NI myDAQ NI myDAQ has fixed +-15V supplies (32 mA) and +5V (100mA), where AD2 has 0...5V and 0...-5V voltage outputs (700mA max with external power supply) => point for ??? Ni myDAQ has 8 digital IO, where AD2 has 16 of them. Also AD2 IOs can be controlled much faster than ones in myDAQ => point for AD2 This is a fast comparison of a key features. Full documentation of each device are available here: https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual http://www.ni.com/pdf/manuals/373061f.pdf Summing up all above (in my opinion): AD2 is a better choice for debugging fast analog and analog/digital circuits. A software adds a great value by allowing various measurements and tools without any need of programming. Also an interface for python scripting allows designing own applications. There is also LabVIEW interface provided. You can always see all these functions in interactive demo - just download recent Waveforms software. https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/start NI myDAQ offers much slower I/O and less digital channels. At the other hand it can be used as off-the-shelf multimeter`. It also includes basic software and interface for LabVIEW, but lacks for example interface control (I2C, SPI, ...). http://www.ni.com/tutorial/11431/en/ Also AD2 can be purchased in reduced price for academic use. This is of course my private opinion on these devices - you have to decide which one to buy by analyzing use cases.
  6. 1 point

    XADC samples issue

    Hi @train04, To tag someones on the forums you need to use the @ symbol and select their name when typed afterward like @train04. cheers, Jon
  7. 1 point
    @MauroChimenti Unfortunately we don't have Linux examples for the Pmod IP cores. In general, for devices that have good Linux support you should modify system-user.dtsi in your petalinux project to load the required drivers. Often times you will need to add the device as a child node of an existing I2C or SPI bus. To find out if the external device you are trying to use has drivers in the kernel, look for a document that corresponds to it here: https://github.com/Digilent/linux-digilent/tree/master/Documentation/devicetree/bindings . If you find one, then it will describe what your device tree will need to look like in order for the driver to get loaded. For devices that don't seem to have good linux support, I would look around for petalinux examples that describe how to use /dev/mem or UIO to gain access to the register maps of devices in the PL. From there it will be a matter of porting any existing SDK examples to use the mmaped files to access the registers.
  8. 1 point
    @fandrei I'll admit I haven't used a Linaro image in a while, but I used to start by finding an armhf image here that seemed suitable for my needs: https://releases.linaro.org/debian/images/ . Here is one that is an example of a good, light-weight desktop that is built around Ubuntu 16.04 LTS: https://releases.linaro.org/debian/images/alip-armhf/16.04/linaro-jessie-alip-20160428-22.tar.gz . Then I would do the following to get it to work with my Petalinux system: 1) Set the root file system to "SD" using petalinux-config. Follow the instructions here to do this, but stop before you get to the "dd" command: https://github.com/Digilent/Petalinux-Zybo-Z7-20/blob/master/README.md#configure-sd-rootfs . 2)Download the root fs from Linaro and extract it 3)Copy the contents of the extracted archive to the second partition of your SD card using "sudo rsync -a". The root of second partition should look like a standard Linux root filesystem if done correctly (/lib, /usr, /home, /mnt, /media, ...). 4) Execute "sync" to ensure all data is copied to the SD card, then unmount both partitions and eject it from your computer. In my experience that used to work most of the time, but you need to make sure you are using a kernel that is pretty close to the one that is expected to be packaged with the image. Also, you will need to manually copy over any kernel modules you need from petalinux.