I2C with MCP23016

[sebastien]

Hi melanie,
the mcp is on portc.3 and 4 for SDA SCL, and thats it. All vss & vdd's are connected and address pins are all grounded.
I've seen those code samples and I inpired my code from them, but it doesn't want to work...grrrr. I don't get anything on the outputs of the MCP.
I really think it is more a clock issue, on the MCP, than an I2C problem. I've tested other I2C devices and they work, they do not need an external RC.

The datasheet says 33Pf and 3.9KOhms for a res and condo between clk pin of the mcp and VSS,VDD.
That should give a 1Mhz clock on test pin, but that clock is very unstable here, and i can't clean it out.

Regards

[eggman]

I ones worked with those chips, I only had it working without the 33 pF capacitor. The MCP23017 seems a better choice, it does not need an external capacitor.

[Acetronics2]

Hi, Sebastien

an interesting reading: Microchip AN 245 ...

Alain

[sebastien]

Hi, Sebastien

an interesting reading: Microchip AN 245 ...

Alain

Seen that appnote and did not find new info compared to the datasheet.
But thanks anyway

[sebastien]

I ones worked with those chips, I only had it working without the 33 pF capacitor. The MCP23017 seems a better choice, it does not need an external capacitor.

Yeah I prefered the 17's but i could not grab that chip at my local store so gone for the 16. I will try without the cap. Thanks for that tip

I'm now managing to do it with the philips component, but it has only 8, so i will have to make 2 other SDA, SCL lines.