How to disable shield electrode thru firmware? (CY8C21534B)

[Anonymous]

Hi All,

   

I'm designing a capsense application with shield electrode implemented for CY8C21534B.

   

I saw in one of the documentation saying that it is recommended to "drive the shield only during a scan, additional code in the firmware is needed". Will someone help to share with me the code that was meant for this function?

   

I'm guessing it is the CSD_DisableSensor function... but need comfirmation or other option (if any).

   

===========================================================================

   

CSD_DisableSensor

   

Description:
Disables the sensor selected by the CSD_wGetPortPin() function. The drive mode is changed to
Strong (001). This effectively grounds the sensor. The connection from the port pin to the Analog-
MuxBus is turned off. The function parameters are returned by CSD_wGetPortPin() function.

   

===========================================================================

       

Thanks!

[pushekm_21]

When a shield signal is routed on the hatch pattern then the signal is always driven whether sensor is scanned or not because the shield signal is a free running clock. You can stop this clock by using a couple of additional line of codes, here is a code snippet:

       

//Configure the drive mode to Strong

   

PRT1DM2 |= 0x80;

   

PRT1DM1 |= 0x80;

   

PRT1DM0 &= ~0x80;

   

CSD_ScanAllSensors();

   

//Configure the drive mode to High Impedance Analog

       

PRT1DM2 &= ~0x80;

   

PRT1DM1 &= ~0x80;

   

PRT1DM0 |= 0x80;

       

Best regards,

   

Pushek

[Anonymous]

Thanks. I check in the technical reference, I think you interchanged between Strong and High Impedance Analog... will you please confirm? I assume the example below is for Port 1 pin[7] right?

       

//Configure the drive mode to Strong

   

PRT1DM2 &= ~0x80;

   

PRT1DM1 &= ~0x80;

   

PRT1DM0 |= 0x80;

       

CSD_ScanAllSensors();

       

//Configure the drive mode to High Impedance Analog

   

PRT1DM2 |= 0x80; 

   

PRT1DM1 |= 0x80;

   

PRT1DM0 &= ~0x80;

[Anonymous · Accepted solution]

 Yes,the code snippets have been intergchanged for strong and high impedance analog mode.

   

The below code sets the mode for P1.7 (Port 1pin[7])

       

//Configure the drive mode to Strong

   

PRT1DM2 &= ~0x80;

   

PRT1DM1 &= ~0x80;

   

PRT1DM0 |= 0x80;

       

CSD_ScanAllSensors();

       

//Configure the drive mode to High Impedance Analog

   

PRT1DM2 |= 0x80; 

   

PRT1DM1 |= 0x80;

   

PRT1DM0 &= ~0x80;