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NHS3152 power only from NFC field and load Capacitor

Question asked by Tom Sander on Dec 7, 2018

Hello,

 

I would like to power the NHS3152 chip only through the NFC field and perform a measurement with it. Unfortunately the measurement seems to consume too much current, so I inserted a capacitor (100µF) between PIO0_7 (high-drive-pin) and ground. Now I want to charge this capacitor through the field first and then use the stored energy of the capacitor plus that of the field to perform a measurement. I have created the following program for this purpose:

 

int main(void)
{

   // TODO: Load Capacitor

   Board_Init();


   Chip_IOCON_Init(NSS_IOCON);
   Chip_GPIO_Init(NSS_GPIO);

 

   Chip_Clock_Clkout_SetClockSource(CLOCK_CLKOUTSOURCE_SYSTEM);

 

   Chip_IOCON_SetPinConfig(NSS_IOCON, IOCON_PIO0_7 , IOCON_FUNC_0 | IOCON_RMODE_INACT | IOCON_LPF_DISABLE | IOCON_CDRIVE_FIXEDVOLTAGE | IOCON_DDRIVE_ULTRAHIGH);

 

   Chip_GPIO_SetPinDIROutput(NSS_GPIO, 0, 7);

   Chip_GPIO_SetPinOutHigh(NSS_GPIO, 0, 7);

   Chip_Clock_System_BusyWait_ms(300);

 

   GetData();
   Chip_NFC_Init(NSS_NFC);
   NDEFT2T_Init();
   sendData();

   return 0;
}

 

However, this does not work yet. I want to read a NDEFT message with a smartphone. Furthermore I noticed while measuring the voltage over the capacitor that it rises to approx. 1.8 Volt. However, not every device seems to have enough power to reach this voltage. My question is whether I have the pins correctly driven or whether I still have other configurations to make.

 

Many thanks in advance.

 

Yours sincerely,

 

Tom

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