I am trying to expand the number of UART ports I have available on a nRF52832 microcontroller using an SC16IS752 attached by SPI. However I don't manage to get responses back from the SC16IS752.
When I set CS to a low level SC16IS752 raises the MISO line to a high level. It stays at that level until after CS went high again. So I'm always continuously reading 0xFF on the SPI MISO line. It kind of looks like SC16IS752 is not seeing any clock signal on CLK. However I can measure the CLK signal of 4 MHz is present..
Any idea what else could result in this behaviour of the SC16IS752?
Edit: Problem solved. The RST line had a low level. After adding a 1K pull up to it everything was working.