Hello, I want to control a milling machine by computer under Windows XP SP2 in real time (For other reasons I cannot use Dos or Unix). The amount of datapoint can be very large (up to GB). So my idea was to store the data on a large USB Stick (not in real time) and then read and process the data it with a controller in order to generate the commands for the stepping motors (in realtime). Is there any way I can do this? (PIC controllers prefered) What hardware (Usb Stick + Interface to controller) can I use? How can I realize a Communtication directly to the Controller via USB? What about PC Drivers? do you have any examples that I can try out myself? thank you, Spaceman Spiff
Many microcontrollers have USB interfaces, so it could easily read data off the USB drive. I haven't used USB yet, but I often use PIC and TI ARM Cortex-M3 controllers and they both have it available.
Simply having an USB interface is not sufficient. Most Controllers equipped with an USB capability are slaves. To read from USB mass storage, you need host (or OTG) capabilities which require a lot more than a simple slave device offers.
Depending on your speed requirements, I'd try an SD Card. SD card libraries are available for most µcontrollers and are much simpler to interface than an USB thumb drive.
You should have a look at STI100. Its an USB Interface, which can easily be used for reading / writing data on a usb Stick.
Thank you for your replies! do you mean this http://www.elv.de/ELV-STI-100-Interface-fuuml;r-USB-Sticks,-Komplettbausatz/x.aspx/cid_74/detail_10/detail2_20659/flv_/bereich_/marke_ discussed Beitrag "USB-Stick-Interface STI 100" ? the sti100 looks very promising but I need some time to try to think about it. I like the SD card Idea as well. Do you have an example? I do not know if an USB interface to the controller would handle the realtime problem. - a mass storage device would be better. any other ideas, examples schematics, codes?
Storage is one option. I think you need to calculate your data rate first: how much data do you need to read per second to control the machine? If we are talking one GB per day its much different from one GB per minute, right? I would probably go for an SD card as well, provided that the interface can handle it. The SD interface comes in two flavors: simple, serial SPI and a much faster 4-bit parallel variant. The typical library only implements the serial variant. Your actual problem I would probably address in a different manner: - use one controller per axis - use an SPI to feed data to the axis controllers from a machine controller - us a network interface to feed the data from the PC to the machine controller. Depending on speed requirements the controllers could be: machine controller: pollin AVR net-IO http://www.pollin.de/shop/dt/NjI5OTgxOTk-/Bausaetze/Diverse/AVR_NET_IO_Fertigmodul.html or rather the Webmodule by Ulrich Radig http://www.ulrichradig.de/home/index.php/avr/avr-webmodule good starting points if speed requirements are not too high. For higher data rates and larger memory buffers, I would consider a "larger" controller like http://www.embedded-projects.net/index.php?module=artikel&action=artikel&id=54 This can integrate the axis controllers as software (output to port pins directly) or use separate controllers to create loop-control and maintain precise timing. The speed that the windows machine can transmit over Ethernet should be fast enough on /average/, even though Windows can not provide real-time behavior. The machine controller can implement the buffer required to even-out the average speed to a constant speed. Again: depending on your data rate, a small buffer (such as the Atmega32 or 644 can provide with its internal RAM) may be sufficient, if a larger buffer is required for evening out the Windows processing jitter, the ARM controller with megabytes of space will be easier to fulfil the requirements. hope, this helps hase
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