On 03/02/2014 01:01 PM, Simon Clubley wrote:> On 2014-03-01, Tim Wescott <tim@seemywebsite.please> wrote: >> On Sat, 01 Mar 2014 09:52:38 +0100, Arlet Ottens wrote: >>> >>> You could implement a CDC class device, and use the standard drivers. >> >> This is a really useful thread to me, because I didn't know nuthing about >> this CDC device class stuff -- does Windows automatically try to hook it >> up to a COM port so you can just pretend its serial, or is there some >> other API that you have to use? >> > > Assuming we are talking about the CDC ACM interface, there are a couple > of things you need to be aware of: > > 1) I've seen reports the Windows CDC ACM drivers are not as good as they > should be. However, be aware that's hearsay: I have no experience with > the Windows CDC ACM drivers. (Also, those reports were about WinXP IIRC; > I don't recall seeing anything about Windows 7). > > 2) There's no way for the CDC ACM device to communicate the CTS status > back to the USB host; it's not part of the CDC ACM specification.Since the USB protocol has its own flow control, the lack of CTS shouldn't be too bad, especially when you integrate the USB functionality on the same controller that handles the data.
Thuraya XT satphone - what USB chip is used?
Started by ●February 28, 2014
Reply by ●March 2, 20142014-03-02
Reply by ●March 3, 20142014-03-03
On Sun, 02 Mar 2014 12:01:42 +0000, Simon Clubley wrote:> On 2014-03-01, Tim Wescott <tim@seemywebsite.please> wrote: >> On Sat, 01 Mar 2014 09:52:38 +0100, Arlet Ottens wrote: >>> >>> You could implement a CDC class device, and use the standard drivers. >> >> This is a really useful thread to me, because I didn't know nuthing >> about this CDC device class stuff -- does Windows automatically try to >> hook it up to a COM port so you can just pretend its serial, or is >> there some other API that you have to use? >> >> > Assuming we are talking about the CDC ACM interface, there are a couple > of things you need to be aware of: > > 1) I've seen reports the Windows CDC ACM drivers are not as good as they > should be. However, be aware that's hearsay: I have no experience with > the Windows CDC ACM drivers. (Also, those reports were about WinXP IIRC; > I don't recall seeing anything about Windows 7). > > 2) There's no way for the CDC ACM device to communicate the CTS status > back to the USB host; it's not part of the CDC ACM specification. > > Microchip have a MCP2200 IC which implements the CDC ACM protocol; they > handled this problem by implementing hardware flow control on the IC > itself.If I did this I'd just be removing an FT230X and plumbing those wires straight to a chip that can handle USB. The thing that really decided me on using the FT230X on this board rather than the on-board resources of the STM32F303 were that the FT230X uses about 80% of the board area of a 7mm x 5mm crystal, and the only thing driving the requirement to have a crystal was the need for USB. It's way space-constrained -- I'm down to 2.5 postage stamps, and I'd certainly be happier at 1.5 or less. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●March 4, 20142014-03-04
Tim Wescott <tim@seemywebsite.really> writes:> On Sun, 02 Mar 2014 12:01:42 +0000, Simon Clubley wrote: > >> On 2014-03-01, Tim Wescott <tim@seemywebsite.please> wrote: >>> On Sat, 01 Mar 2014 09:52:38 +0100, Arlet Ottens wrote: >>>> >>>> You could implement a CDC class device, and use the standard drivers. >>> >>> This is a really useful thread to me, because I didn't know nuthing >>> about this CDC device class stuff -- does Windows automatically try to >>> hook it up to a COM port so you can just pretend its serial, or is >>> there some other API that you have to use? >>> >>> >> Assuming we are talking about the CDC ACM interface, there are a couple >> of things you need to be aware of: >> >> 1) I've seen reports the Windows CDC ACM drivers are not as good as they >> should be. However, be aware that's hearsay: I have no experience with >> the Windows CDC ACM drivers. (Also, those reports were about WinXP IIRC; >> I don't recall seeing anything about Windows 7). >> >> 2) There's no way for the CDC ACM device to communicate the CTS status >> back to the USB host; it's not part of the CDC ACM specification. >> >> Microchip have a MCP2200 IC which implements the CDC ACM protocol; they >> handled this problem by implementing hardware flow control on the IC >> itself. > > If I did this I'd just be removing an FT230X and plumbing those wires > straight to a chip that can handle USB. > > The thing that really decided me on using the FT230X on this board rather > than the on-board resources of the STM32F303 were that the FT230X uses > about 80% of the board area of a 7mm x 5mm crystal, and the only thing > driving the requirement to have a crystal was the need for USB.> > It's way space-constrained -- I'm down to 2.5 postage stamps, and I'd > certainly be happier at 1.5 or less.There are some crystal-less STM32 parts IIRC -- John Devereux
Reply by ●March 4, 20142014-03-04
John Devereux <john@devereux.me.uk> writes:> Tim Wescott <tim@seemywebsite.really> writes: > >> On Sun, 02 Mar 2014 12:01:42 +0000, Simon Clubley wrote: >> >>> On 2014-03-01, Tim Wescott <tim@seemywebsite.please> wrote: >>>> On Sat, 01 Mar 2014 09:52:38 +0100, Arlet Ottens wrote: >>>>> >>>>> You could implement a CDC class device, and use the standard drivers. >>>> >>>> This is a really useful thread to me, because I didn't know nuthing >>>> about this CDC device class stuff -- does Windows automatically try to >>>> hook it up to a COM port so you can just pretend its serial, or is >>>> there some other API that you have to use? >>>> >>>> >>> Assuming we are talking about the CDC ACM interface, there are a couple >>> of things you need to be aware of: >>> >>> 1) I've seen reports the Windows CDC ACM drivers are not as good as they >>> should be. However, be aware that's hearsay: I have no experience with >>> the Windows CDC ACM drivers. (Also, those reports were about WinXP IIRC; >>> I don't recall seeing anything about Windows 7). >>> >>> 2) There's no way for the CDC ACM device to communicate the CTS status >>> back to the USB host; it's not part of the CDC ACM specification. >>> >>> Microchip have a MCP2200 IC which implements the CDC ACM protocol; they >>> handled this problem by implementing hardware flow control on the IC >>> itself. >> >> If I did this I'd just be removing an FT230X and plumbing those wires >> straight to a chip that can handle USB. >> >> The thing that really decided me on using the FT230X on this board rather >> than the on-board resources of the STM32F303 were that the FT230X uses >> about 80% of the board area of a 7mm x 5mm crystal, and the only thing >> driving the requirement to have a crystal was the need for USB. > >> >> It's way space-constrained -- I'm down to 2.5 postage stamps, and I'd >> certainly be happier at 1.5 or less. > > There are some crystal-less STM32 parts IIRCSorry, I meant parts designed to work with USB without a crystal! -- John Devereux