GPIO Current Drive

[lance338]

My application uses the nRF51822 with a GPIO configured as output and another GPIO is configured as input. Connected to the GPIO_OUT is a resistive load (Rload) which then connected to GPIO_IN. When GPIO_OUT drives a '1' and if the load has low resistance, we would expecte a '1' at GPIO_IN.

GPIO_OUT ------------------ Rload -----------------------GPIO_IN 

Per spec, the VDD is 3.3V.

With GPIO_PIN_CNF_DRIVE is set to S0S1, the spec say this would drive 0.5mA. The max Rload measdured to be around 6K ohm.

When GPIO_PIN_CFG_DRIVE is set to H0H1, we get the same result.

I would expect the high-drive to allow for more resistance on the load. 

Is this correct? Why would the S0S1 and H0H1 have the same result?

[Kenneth]

Hi,

The drive strength configure the max current the GPIO _may_ provide, to sink or source external circuitry.

In this case I think you have a 6Kohm resistor in series with an input pin with very high impedance (>>1Mohm). So there will be close to no current floating through the 6Kohm resistor.

Best regards,
Kenneth

[lance338]

Thanks Kenneth. Our goal is to be able to detect '1' at the input gpio with a load of 20K ohm. Do you have any suggestion to achieve that?

[awneil]

See below about your meaning of "load".

As a straightforward resistor between OUT and IN, it should work - so there must be something else going on...