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. S=
o
> after the master 'releases' the clock to go high, it needs to wait until
> 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 t=
o
> > 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 configur=
ed
> > > the ANSELC register to disable analog input in RC7?
> > >
> > > Using the TRIS register to switch a pin between an input, or an outpu=
t
> > > with a logic 0 level set is a common way of simulating an open-drain
> > > output if this function is not support in hardware. The code you used
> > > was very likely written for an old 14 bit part (16C/16Fxx etc.) which
> > > 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 th=
e
> > > > 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 i=
n
> > > > question. And that's why I can write to the I2C bus just fine, but
> > > reading
> > > > from it I am stumbling. For my bit read function I change the port
> 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 t=
o
> be
> > > > obsoleted soon.
> > > > --
> > > > Sincerely,
> > > >
> > > > James Burkart
> > > > *925.667.7175*
> > > >
> > >
> > > --
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> > >
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