A device I am working requires that I can manually drive the same 2 lines that are connected to an I2C Fixed Function Block.

I have a fixed function I2C Slave block connected to a 2-pin Bidirectional 'Pins' component.

The device it is connected to sends a message by I2C then goes into a passive state, tri-states it's two lines and waits for a specific signal shape on the 2 lines.

I have attached a picture of the scehmatic from Psoc Creator.

In order to communicate with this device, my PSoC 5 design has the I2C Slave block as described above, and when the special message is received I want to be able to drive the 2 lines which are used for SCL and SDA in a specific sequence.

I see that there are APIs generated for the 2 pins, and for the pin block, but when I use the generated API's I do not see any output on the pins - they seem to be constantly driven  high, even if I do: RPC_PINS_Write(0x00);

I tried connecting a MUX but the fitter gave an error saying there were multiple drivers on the line. Probably becuase the pins are bi-directional.

Is there anyway to drive the SCL and SDA lines directly? Can I change my schematic in some way that the I2C will work, then I can disable it and drive the lines directly?

Hi KennyMiller,

Using of MUX would not have worked in this case as the I2C pins are bidirectional whereas digital MUX terminals are unidirectional (from input to output only, depending upon the select lines chosen).

The Bypass Register PRT_BYP for a Port is used to determine if the output is from the data output register or internal sources such as digital global bus.

If the bit is set to '1', then digital system interconnect (DSI) drives the corresponding port pin.

If set to '0', then the Port Logic Data Register drives the corresponding port pin.

The drive mode should be set to "Strong Drive" when used as output. The code snap shot is as shown below. The pins are toggled in this example.

The sample project is attached along with this comment.

 Thank you, dasq, that was very helpful.

-Kenny

You're welcome 

 Hi Dasg,

Could you tell me why you are setting it into strong mode here? Can't we use it as an output pin in open drain configuration itself?

Hi PSoC Lover,

Yes, you can use the pins in Open drain Drive Low / High configuration too.

In the code snippet above, I assumed that KennyMillar wants to be able to drive the pins both High and Low.

If open drain configuration is used, then Pull-up or Pull-down resistors should be used depending upon whether the pin are in open drain drive low or drive high configuration.