pca10056 vddio and REGOUT0 setting

[Julie H]

Greetings -

I am working on a peripheral-heavy project. Many of the devices seem to work Just Fine with VDDio of 1.8 volts. On device seems to be having fits and I need to rule out a low "logic 1" voltage.

The PCA10056 I have has the "EXTSUPPLY" register in the UICR set to "true" (0x1) and "REGOUT0" having a value with the low-order 3 bits set to 0x4. According to the documentation for the device, the result SHOULD be that VDDio is 3.0 volts.

If I assert a GPIO pin and measure the voltage I see 1.80 volts. If I hook up a logic analyzer and look at GPIO pins that are being used for SPI and I2C peripherals, I see 1.80 volts.

Update: I have tested other code, including the "usbd" example, and output voltage is 3.0 volts, as expected. The key difference is that my code is using BLE functions through the SoftDevice and the "usbd" example doesn't.

Help?

[endnode]

Hi Julie,

From what I see in nRF52840 OBS changing EXTSUPPLY and REGOUT0 registers make sense only in "high voltage mode". Are you sure you run the chip in that configuration? I actually doubt as this mode should not support 1.8V (at least that's what power fail comparator suggests).

Cheers Jan

[Julie H]

The GPIO pins definitely don't have a high reference voltage of VDD, which is 3.0 volts. Here's the problematic text --

GPIO levels

The GPIO high reference voltage always equals the level on the VDD pin.

In normal voltage mode, the GPIO high level equals the voltage supplied to the VDD pin, and in high voltage mode it equals the level specified in the register REGOUT0 listed in UICR — User information configuration registers.