http://forums.leaflabs.com/topic.php?id=565 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:09:32 +0000 http://bbpress.org/?v=1.0.2 q http://forums.leaflabs.com/search.php http://forums.leaflabs.com/topic.php?id=565#post-3081 Sat, 11 Dec 2010 15:26:41 +0000 x893 3081@http://forums.leaflabs.com/ <p>It's possible but only one problem - number of endpoints in STM32 chip. You can adopt Versaloon project for Maple support if you need more than one USB device on Maple. </p> http://forums.leaflabs.com/topic.php?id=565#post-3079 Sat, 11 Dec 2010 11:41:05 +0000 gbulmer 3079@http://forums.leaflabs.com/ <p>soundcyst - great question. I'd love to know the answer to that too. </p> <p>When I read the USB specs, e.g.<br /> <a href="http://www.usb.org/developers/docs/" rel="nofollow">http://www.usb.org/developers/docs/</a><br /> I don't see what would prevent it. Though it does seem to add complexity.</p> <p>A Hub has to present itself to the USB host 'properly', including having its own USB Device class and control endpoint. So, I assume being a hub would 'consume' the STM32F's control end point, but I don't see why that might be a problem.</p> <p>The USB spec. (usb_20.pdf) includes chapters on a Hub, which is more than 1/4th the main document (123 of 420 pages). So there is some complexity in there. </p> <p>There is a chunk of that USB hub documentation around *not* doing certain USB transactions during periods when a real USB device is doing a transaction, but that shouldn't happen when the device is just faking being a hub.</p> <p>I have assumed their is more to it, but mainly because of the amount of documentation in the USB spec.</p> <p>According to the USB spec:<br /> "4.8.2.2 Functions<br /> A function is a USB device that is able to transmit or receive data or control information over the bus. A function is typically implemented as a separate peripheral device with a cable that plugs into a port on a hub. <strong>However, a physical package may implement multiple functions and an embedded hub with a single USB cable. This is known as a compound device. A compound device appears to the host as a hub with one or more non-removable USB devices. </strong>" (My emphasis)</p> <p>I assume the 'non-removable USB devices' is the unique part of 'compound device', but I haven't been able to pin that down. </p> <p>I would have imagined that 'compound device' could become 'invisible' to the host if it were a hub + several USB devices, and the software enumerated them as if they were being plugged in. </p> <p>I assume condensing the devices into a hub+spoofed devices would require each device to be enumerated, and get polled. Enumeration would take longer at bootup, and polling would take longer. If it were only a few USB devices, I wouldn't have thought this would be a big performance impact.</p> <p>It is extra software complexity though. For it to have some benefit, it'd need to implement a USB Hub and at least two USB Devices.</p> <p>From the perspective of a minimal bootloader and debug infrastructure, being a single USB device would be simpler. Candidate devices which are widely supported, and relatively understandable include CDC virtual serial. There are others, including HID, but I don't know how I would 'open' a HID device from the host PC, and make any use of the device. Using a USB CDC virtual serial is pretty well understood.</p> <p>But having a framework which would support 'plugging in' combination's of USB Devices looks like a good idea for general development.</p> <p>{whine: I would *much* prefer this sort of functionality in preference to LeafLabs creating and supporting Yet Another IDE} </p> http://forums.leaflabs.com/topic.php?id=565#post-3075 Fri, 10 Dec 2010 21:26:18 +0000 soundcyst 3075@http://forums.leaflabs.com/ <p>With the bootloader, DFU, and CDC issues that have arisen, and the discussion of adding another chip a la Arduino, I thought I'd pose a question: would it be a good idea (see: easy, effective, not processor hungry) to have the STM32's USB functionality pretend to be a hub to the host? In this way, the chip could have a DFU device and a CDC device, or also an HI device, or Audio device, etc. "attached to the hub" without running into the Windoze and Mac issues of driver attachment and IADs. Or could it? I'm not well-enough versed in USB to know if this sort of spoof would be effective to the host, and cheap enough to be worthwhile on the device, but I thought I'd ask.</p> <p>Or if the STM32 doesn't support it, perhaps the helper chip could be a hub controller that would support splitting the devices? (This option seems trickier than the former)</p> <p>Thoughts? </p>