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SPI interword gap
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SPI interword gap
by David Baur
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I'm attempting to send 4K 16 bit words over the SPI bus at 24Mhz. Theoretically it possible, but I've noticed that there is a clock gap between words. Does anyone have any experience on how to reduce or eliminate this gap? I've discovered a 'turbo' mode, but haven't really noticed a reduction in gap size.
Thanks -- David G. Baur 505 286-0293 h 505 284-8031 w 505 362-4443 c ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: SPI interword gap
by jumpnowdev
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The Linux SPI subsystem is not designed for things like this.
It's based on workqueues. http://www.linuxjournal.com/article/6916 Use the OMAP3 McBSP controller instead. McBSP3 can be mux'd out pins 27-30 on most of the expansion boards (gpio 144-147) I've used it in a number of projects and you can get very good, deterministic performance from it. It can do 'SPI' protocol, but with only one 'slave' device. -- View this message in context: http://gumstix.8.n6.nabble.com/SPI-interword-gap-tp4964698p4964699.html Sent from the Gumstix mailing list archive at Nabble.com. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: SPI interword gap
by William Hue-2
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David,
If you make use of the hardware FIFO, there should be no inter-word gaps. If you still get the occasional gap with the FIFO, then using DMA should get rid of that. Are you using the standard driver or a custom one that you wrote? William On 2012-06-22 12:46, David Baur wrote: > I'm attempting to send 4K 16 bit words over the SPI bus at 24Mhz. Theoretically it possible, but I've noticed that there is a clock gap between words. Does anyone have any experience on how to reduce or eliminate this gap? I've discovered a 'turbo' mode, but haven't really noticed a reduction in gap size. > > Thanks > > -- > David G. Baur > 505 286-0293 h > 505 284-8031 w > 505 362-4443 c > > > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > > > > _______________________________________________ > gumstix-users mailing list > gumstix-users@... > https://lists.sourceforge.net/lists/listinfo/gumstix-users ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: SPI interword gap
by AKS-4
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Hi
How about bit bashing, switching on and off the GPIO ports instead of using SPI hardware registers? Then you can control everything. On 6/22/12, David Baur <dgbaur@...> wrote: > I'm attempting to send 4K 16 bit words over the SPI bus at 24Mhz. > Theoretically it possible, but I've noticed that there is a clock gap > between words. Does anyone have any experience on how to reduce or > eliminate this gap? I've discovered a 'turbo' mode, but haven't really > noticed a reduction in gap size. > > Thanks > > -- > David G. Baur > 505 286-0293 h > 505 284-8031 w > 505 362-4443 c > ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: SPI interword gap
by Akram Hameed
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Pretty sure he'd never manage 24MHz bitbashing. If he did, I'd be
surprised! -----Original Message----- From: AKS [mailto:aungkyas@...] Sent: Saturday, 23 June 2012 10:01 AM To: General mailing list for gumstix users. Subject: Re: [Gumstix-users] SPI interword gap Hi How about bit bashing, switching on and off the GPIO ports instead of using SPI hardware registers? Then you can control everything. On 6/22/12, David Baur <dgbaur@...> wrote: > I'm attempting to send 4K 16 bit words over the SPI bus at 24Mhz. > Theoretically it possible, but I've noticed that there is a clock gap > between words. Does anyone have any experience on how to reduce or > eliminate this gap? I've discovered a 'turbo' mode, but haven't > really noticed a reduction in gap size. > > Thanks > > -- > David G. Baur > 505 286-0293 h > 505 284-8031 w > 505 362-4443 c > -------------------------------------------------------------------------- ---- Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: SPI interword gap
by David Baur
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I'm using the mcspi low level driver and code based on Scott Ellis' spike protocol layer. I turned on 'Turbo' mode which did reach the speed requirement.
But subsequently, my mmc ssd failed and I can no longer create a kernel that talks over the ethernet 'Invalid chip ending'. And after much consternation, now I can't even build a kernel that starts. I'm losing my faith in the Gumstix boards. dave On Fri, Jun 22, 2012 at 5:27 PM, William Hue <william@...> wrote: David, -- David G. Baur 505 286-0293 h 505 284-8031 w 505 362-4443 c ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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