I2C Slave with a PIC

[tacbanon]

@ DT, Thanks for the update..I will find time to play with it(I2C multiple slaves) this weekend(so many work, little time to play )

Kind regards,
tacbanon

[ralfmayr]

Hi all,
for info to all: I have the code from Aretti here on a 18F25K22, works fine with one slave on one master. When i connect more slaves (up to 31) i get the effect that a NACK comes right behind the address, the SDA line is high during the 9th clock cycle... my bus is about 70cm long (long backplane) and i use a 3.3k on the i2c bus. It seems that this "NACK" effect is coming sporadic, does someone tried to do the same like me?
Regards,
Ralf

[ralfmayr]

Hi again,
found the bug: the bus i am using is splitted in two 2 x 25cm long busses which is not the best solution. Sometimes because of layout reasons it must be done this way. In this case two 100 Ohm resistors close to the Master in series with SDA and SCL and pullup's 2 x 10kOhm at both ends of the splittet bus make the bus working fine. I checked the timing with a logic analyser and the quality of the signals with a scope, both ok, no glitches or other dirty effects. Hope this help others having same trouble. I must say best solution is always making the bus from one end to the other end in one direction, i tested this also with 80cm. Adding also two 100 Ohm resitors in series with SDA and SCL close to the master makes the signal quality better also.
Both versions run with 80kHz very fine now.
Regards,
Ralf