Quote Originally Posted by CLAUDY
In fact the Pcb is done simply for the moment to get used to the MCP23017 that will serve me to something else after.
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Are you saying the MCP23017 is NOT used at the moment? Why issue an I2C command to something inactive? Do you have LEDs connected on the MCP23017?


Quote Originally Posted by CLAUDY
The PCB is composed of 8 LED simply placed on Port A and 8 LED placed on port B.
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Code:
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?