Mcp 23017 and Pic 16f877

[mister_e]

sda var porta.0 'sda est sur le porta.0
scl var porta.1 'scl est sur le porta.1

So you have 16 LEDs on ports A and B, but you also use Port A for I2C communication?

Why not use Port C.3 for SCL and Port C.4 for SDA (PIC 16F877 datasheet pinout p.3) to avoid interfering with your LEDs?

Actually If I understand properly, it is worst than this. If the LED are connected to Ground on the I2C line, they Screw-up the line as they have to be Pulled-high (hi-z) but the LED LOAD it to gnd.

Get rid of the LED on those I/O or, like BobyBert said, move the I2C line elsewhere (it doesn<t need to be on a specific SCL, SDA PIC line as you're using I2CREAD/I2CWRITE who's not using the built in SSP module). You want the I2C line on their own I/O.

[CLAUDY]

Hello,

Thank you for your answers.

When I speak of the port A and B have ports MCP23017 and not PIC.
The PIC used is a 877A.
The PIC controls only the LCD and I use the port A of the PIC to bond with the I2C MCP23017.

A big thank you for your help.

Soon

Claudy

[Acetronics2]

Hi, Claudy

Following your adventures on many forums for a moment ... I still miss a small thing : YOUR USED SCHEME ...

Alain

[CLAUDY]

Hello Alain,

I still have not found the solution.

Here's a quick diagram as requested.Printing TEST MCP23017-sch.pdf

Thank you

Claudy

[Acetronics2]

Looks there's also a missing register named IOCON in the settings.

Alain

[CLAUDY]

Hello everyone,

Ok it works!

Bit 7 of Port A and B of the MCP23017 must be 1 before the startup of the program.

And in this case each power program is operating normally the first

Here is the code added.

i2cwrite sda,scl,$40,[iolata,128] 'Output Latch Reg
i2cwrite sda,scl,$40,[iolatb,128] 'Output Latch Reg


If you have comments please.

Thank you

Claudy

[rauloj]

Bit 7 of Port A and B of the MCP23017 must be 1 before the startup of the program.

And in this case each power program is operating normally the first

Here is the code added.

i2cwrite sda,scl,$40,[iolata,128] 'Output Latch Reg
i2cwrite sda,scl,$40,[iolatb,128] 'Output Latch Reg


If you have comments please.

Thank you

Claudy

Hi Claudy!

It's not OLATA/OLATB you are setting 1, but IOCON.
After power-on BANK bit = 0 and IOCON's adr = 0A/0B not OLATA/OLATB's.
After setting IOCON bit 7 to 1 you can use address mapping as described in datasheet table 1-5.

R