Hi James,

I did check your code and didn't see where it actually checks for the clock
to go high (that is, read input and check it, not fixed delay). Didn't
check all of your code though, so I might have missed it.

Good luck.
Joep

Op ma 21 okt. 2019 om 06:44 schreef James Burkart <james@burkartstudios.com
>:

> Thanks Joep,
>
> I appreciate the help. I do understand how I2C works, my questions are
> about my code. The port pins I am using for clock and data are operating =
as
> open drain, so I'm not driving anything high.
>
> --
> Sincerely,
>
> James Burkart
> *925.667.7175*
>
>
> On Sun, Oct 20, 2019 at 4:11 AM Joep Suijs <jsuijs@gmail.com> wrote:
>
> > Hi James,
> >
> > The slave hold the clock low to hold off the master when it needs time.
> So
> > after the master 'releases' the clock to go high, it needs to wait unti=
l
> > the clock line actually is high before it can proceed. This is also the
> > reason you shouldn't drive clock high, only low...
> >
> > Joep
> >
> > Op zo 20 okt. 2019 om 00:23 schreef James Burkart <
> > james@burkartstudios.com
> > >:
> >
> > > I am using pull up resistors on both SCL and SDA. Analog is disabled =
on
> > > RC7. The author of the original code mentions that he wrote the code =
to
> > be
> > > as universal as possible. I understand the reasoning, it's just
> > > implementing it that's giving me issue. So I re wrote the code and am
> > using
> > > the open drain feature of my micro on SDA and SCL. But now I'm trying
> to
> > > successfully read from SDA.
> > >
> > > On Sat, Oct 19, 2019, 4:13 PM Mike <pic.developer@gmail.com> wrote:
> > >
> > > > Do you have pull-up resistors on both SCL and SDA?  Have you
> configured
> > > > the ANSELC register to disable analog input in RC7?
> > > >
> > > > Using the TRIS register to switch a pin between an input, or an
> output
> > > > with a logic 0 level set is a common way of simulating an open-drai=
n
> > > > output if this function is not support in hardware. The code you us=
ed
> > > > was very likely written for an old 14 bit part (16C/16Fxx etc.) whi=
ch
> > > > don't have open-drain outputs.
> > > >
> > > > Regards
> > > >
> > > > Mike
> > > >
> > > > On 19/10/2019 22:49, James Burkart wrote:
> > > > > I wrote up a bit-bang I2C routine to communicate with a couple
> > devices,
> > > > an
> > > > > SSD1306 OLED and an MCP23018 port extender. I'm using a
> PIC18F27K40.
> > > > >
> > > > > I've got the sending data part just fine, but I can't figure out
> the
> > > > > receiving part, including reading acknowledge bits. I, in large,
> > copied
> > > > the
> > > > > code example from a blog post by Calvin Cherry (
> > > > >
> > > >
> > >
> >
> https://calcium3000.wordpress.com/2016/08/19/i2c-bit-banging-tutorial-par=
t-i/
> > > > > ).
> > > > > To be honest, the way he was switching SDA between an input and
> > output
> > > > was
> > > > > confusing to me and so I just enabled open drain on the port pins
> in
> > > > > question. And that's why I can write to the I2C bus just fine, bu=
t
> > > > reading
> > > > > from it I am stumbling. For my bit read function I change the por=
t
> > pin
> > > > used
> > > > > for SDA to an input and read its value through PORTCbits.RC7 but
> it's
> > > > > always reading 0.
> > > > >
> > > > > I'd like to use the hardware I2C but I can't get the MCC code to
> > work,
> > > > > either the Foundation Services version, nor the other one that is
> to
> > be
> > > > > obsoleted soon.
> > > > > --
> > > > > Sincerely,
> > > > >
> > > > > James Burkart
> > > > > *925.667.7175*
> > > > >
> > > >
> > > > --
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