i2C with PIC16F87, need help

[Demon]

...
I am struggling with I2C to communicate between PIC16F877A and a PIC16F87.
...

Olivier,

Do you HAVE to use I2C?

Is there any reason why you couldn't use USART to communicate between the 16F877A and 16F87?

16F87 p.99 section 11 AUSART

The AUSART can be configured in the following
modes:
• Asynchronous (full-duplex)
• Synchronous – Master (half-duplex)

• Synchronous – Slave (half-duplex)

16F877A p.113 section 10 USART

The USART can be configured in the following modes:
• Asynchronous (full-duplex)
• Synchronous – Master (half-duplex)

• Synchronous – Slave (half-duplex)

The acronym is slightly different, but when you read the descriptions, they are the identical.

[Charles Linquis]

You can either use RS-232 or I2C or SPI or PSP or ... to talk between two PICs.

If you use RS-232, and you have only two chips in your little 'network' then it is trivial - just hook TXD to RXD and RXD to TXD. If you send two characters or less, you don't need interrupts - just check for PIR1.5 being set (that is what it is in 18F chips, anyway), then read the characters using HSERIN.

But the problem is - if your chips have only 1 RS-232 port, you have no RS-232 ports left. So, the solution is to use at least one chip that has two RS-232 ports, or to use a chip that has one RS-232 port and one I2C port. Your choice.

My example doesn't use bit-banging. It uses hardware. It uses real interrupts. It works on my chips.