Thu, 24 Nov 2005, by roger@opq.se:
On Thu, 2005-11-24 at 13:18 +0000, JUAN ERNESTO FLORES BELTRAN wrote:
carlos wrote:
You still haven't said what sampling speed you need, but unless it is slow, you will need to save somewhere else first (as fast as posible), and then move to the database as a post process.
Sampling speed will be as slow as possible because of this is a project for the university...not a product for anyone so speed is subject to the designer programming skills and available resources: adquisition data card specifications, programming language, etc...
just to get an idea...what limit is considered "too fast" to save somewhere else before saving into the database?? and what technical reasons would
Depends on the acquisition card. Some intelligently buffer data so an OS can take it when it can. Some only return a current value. So, the requirements of the OS are determined first by the card and secondly by how well the device driver is written.
For best speed you'd probably want to use [a card with] dual-port memory and DMA, so that both the acquisition and processing can occure at the same time. Polling or interrupts is usually way too slow. Like you said, one thread would then directly transfer the data from DP mem to the harddisk (in binary format), while another would read from the disk and send the processed data to your database. Theo -- Theo v. Werkhoven Registered Linux user# 99872 http://counter.li.org ICBM 52 13 26N , 4 29 47E. + ICQ: 277217131 SUSE 9.2 + Jabber: muadib@jabber.xs4all.nl Kernel 2.6.8 + See headers for PGP/GPG info. Claimer: any email I receive will become my property. Disclaimers do not apply.