I2C2 pic18F26k22

[cvargcal]

Hi I am trying use the oled display, but no work in real. simulated yes.
Maybe I need have do it some configuration on this pic?

taken of : https://simple-circuit.com/ssd1306-oled-ccs-c-library/

this the code
Library

[PCM programmer]

Run the i2c scanner program on it. See if it finds the i2c slave at the
expected slave address:
http://www.ccsinfo.com/forum/viewtopic.php?t=49713

[temtronic]

Yes, 1st thing to do with EVERY I2C device, run PCM P scanner program. You may find that the address of the device is '7 bit' mode not the CCS '8 bit' default.
Easy to convert....scanner will find it.
Also...
change the clock to 8MHz, at least for test purposes. I've had some I2C devices not like fast clocks,probably due to wiring, capacitance, wrong pullups.
8MHz has always worked.My current 26k22 project does run at 16MHz but not at 32MHz.

[cvargcal]

Thanks this is the answer


Found
Start:

Start:

Start:
ACK addr: 78

Number of i2c chips found: 1


I change that 7A by 78 but still not work, I have pull up 10k... I think that is not problem

[temtronic]

Check the schematic of the display and see if it has I2C pullups already. Some do, some don't.
To me 10K is too high, for a fast device at 3 volts( I'm assuming both PIC and display are powered from 3 volts....)

To some very basic tests...cut code to read a register, then write to it, then read it back.

Also very carefully check the driver for other addreses other than the base address or variables that refer to the base address.

[cvargcal]

[Ttelmah]

Even 5K6 is large.

I2C is dependant on _current_ in the pull-up. Running off 3.3v, the
current drawn by the pull-up for a given resistor is less.

The pull-ups, have a minimum, and maximum 'range' that can be used.
The maximum is dependant on the bus speed, and the capacitance of
the bus. The lower the resistor, the more capacitance the bus can have.

The minimum resistor value is calculated as:

Rp(min) = (Vcc-Vol(max))/Iol

Iol depends on the devices being used, but I2C requires all devices
to be able to sink at least 3mA. Vol is specified as 0.4v.

The maximum value depends on the bus capacitance, the input
voltage range that has to occur, and the speed of the bus. This
simplifies to:

Rp(max) = tr/(0.8473*Cb)

Where tr is the rise time required, and Cb is the bus capacitance.
For a 400KHz I2C bus, tr is 300nSec.

So for the min calculation, at 3.3v:

(3.3v-0.4v)/0.003 = 966R

Then lets allow for a reasonable bus capacitance. Each chip is going
to have an input capacitance of at least perhaps 5pF. A few inches of
wire and PCB tracks on the display will give at least 20pF, so a nice
safe figure assuming the bus is not too long is to assume 100pF
total.

So

300E-9/(0.8473*100E-12) = 3540R

Sp for a 100pF bus, the minimum resistor value is 966R, and the max
3540R.
Your 5K6 limits your maximum bus capacitance to 63pF. Probably
OK if there is only one device on the bus and it is short. However
not perhaps much margin...

On 5v, 4K7 is a good 'safe bet' resistor, likely to work on most busses.
On 3.3v, 3K3 is the equivalent.

on 5v, 10K, is OK for a _standard mode_ bus (100KHz max). However
for a faster 400K bus, a lower value should be used.

[temtronic]

All the complicated (but serious) math that Mr. T nicely wrote about can be remembered easily.

5 volt PIC use 5K resistors, 3 volt PICs use 3K resistors.

4k7 and 3k3 are 5% resistors and should be laying round everyone's workbench.

The older you get the more you need easy ways to remember stuff !

[cvargcal]

Great information!!
thanks