My network connection has been down for almost a week so I could nit pursue the suggestions you made. Now that I have, I think it is worth going for the hardware solution as there are many places that the parport driver is impacted and it will take a lot of testing. I will still do the i2c for parport but with some time to test properly later.
On 2014-05-18 15:59, Steve Stallings wrote: > Marius, > > The hardware direction control issues may be simpler > than you expect. > > The I2C bus does not use tri-state and direction > control. Rather it uses "open collector" or "open > drain" style outputs with a pull-up resistor. When > it wants to read from an input, it writes a logic > one to that output so that the driver is not pulling > down. > > The resistor pulls up and if there is nothing else > driving the signal, then the input from that same > signal will read as one. If something else connected > to that signal drives the signal to zero, then it > will overcome the pull-up resistor and the input > will read as a zero. > > The standard parallel printer port includes four > signals (pins 1, 14, 16, and 17) that behave in this > same manner and may be usable for direct connection > to an I2C bus. > > Recommended reading: > > http://www.linux-cae.net/Projects/Parallel/Dage/parport.html > > Parallel ports that follow the original IBM-PC design > recommendations will have a 4.7K ohm pull-up resistor. > For many applications this will directly work with the > I2C bus. In a few cases the resistor may be a different > value and in a very few rare cases parallel ports have > been built that use totem-pole drivers for these pins. > > If you are not comfortable with connecting your I2C bus > directly to the parallel port, you can also use external > buffers that are open-collector to achieve the same thing > without needing to control the direction of the parallel > port's data pins. It just requires one more pin from the > parallel port because the data out and data in will need > to be on different pins. See this application note: > > http://www.maximintegrated.com/app-notes/index.mvp/id/3230 > > Do keep in mind that some of the signal paths in a parallel > port interface have an extra signal inversion, so what is > described as a one or zero at the parallel port connector > may show up as the reverse when software reads the interface > registers. > > Regards, > Steve Stallings > www.PMDX.com > > >> -----Original Message----- >> From: Marius Liebenberg [mailto:[email protected]] >> Sent: Sunday, May 18, 2014 4:12 AM >> To: [email protected] >> Subject: Re: [Emc-developers] New function for parport driver required >> >> Partly as you say but it only puts the control lines into >> input mode so >> that the port has 8 out and 9 input lines. To use it as bidirectional >> pins the approach is slightly different. So I have to add the >> bi-directional pins as a config option and then they must be >> handled is >> input or output as required. >> Currently the code only handles input or output mode. I >> started with the >> corrections already and might ask for some testing help later. >> >> One wire will work if we have bi-dir pins. Just need a driver >> comp then. >> Once I have the bi-dir stuff sorted I can continue with the >> I2C driver. >> >> >> On 2014-05-18 09:23, Andy Pugh wrote: >>>> On 17 May 2014, at 22:55, Marius Liebenberg >> <[email protected]> wrote: >>>> I need an added feature for the parport driver namely to >> be able to put >>>> the control pins in bi-directional mode in order to drive >> i2c devices. >>> I think that this is partly implemented already as the "x" mode. >>> >>> It might also be a useful feature for bit-banging onewire. >>> >>> >> -------------------------------------------------------------- >> ---------------- >>> "Accelerate Dev Cycles with Automated Cross-Browser Testing >> - For FREE >>> Instantly run your Selenium tests across 300+ browser/OS combos. >>> Get unparalleled scalability from the best Selenium testing >> platform available >>> Simple to use. Nothing to install. Get started now for free." >>> http://p.sf.net/sfu/SauceLabs >>> _______________________________________________ >>> Emc-developers mailing list >>> [email protected] >>> https://lists.sourceforge.net/lists/listinfo/emc-developers >>> >> -- >> >> Regards /Groete >> >> Marius D. Liebenberg >> +27 82 698 3251 >> +27 12 743 6064 >> QQ 1767394877 >> >> >> -------------------------------------------------------------- >> ---------------- >> "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE >> Instantly run your Selenium tests across 300+ browser/OS combos. >> Get unparalleled scalability from the best Selenium testing >> platform available >> Simple to use. Nothing to install. Get started now for free." >> http://p.sf.net/sfu/SauceLabs >> _______________________________________________ >> Emc-developers mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-developers >> > > ------------------------------------------------------------------------------ > "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE > Instantly run your Selenium tests across 300+ browser/OS combos. > Get unparalleled scalability from the best Selenium testing platform available > Simple to use. Nothing to install. Get started now for free." > http://p.sf.net/sfu/SauceLabs > _______________________________________________ > Emc-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers > -- Regards /Groete Marius D. Liebenberg +27 82 698 3251 +27 12 743 6064 QQ 1767394877 ------------------------------------------------------------------------------ "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE Instantly run your Selenium tests across 300+ browser/OS combos. Get unparalleled scalability from the best Selenium testing platform available Simple to use. Nothing to install. Get started now for free." http://p.sf.net/sfu/SauceLabs _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
