I am new to using the STM32H563, 64 pin package and am trying to implement Dallas 1 wire protocol with a UART.
Initially I was going to use transmit and receive with diode back into Tx, but I saw example using the Half duplex mode of the UART and thought I would give that a go.
However, whenever I change the USART1 pin to open drain (Pin 59 of 64 pin package), the line which is pulled up by a 4k7 resistor drops to about 200mV. If I try to transmit with the UART, I can see the Open drain pulling from 200mV down to ground as the data goes through. If I place another 4k7 pullup in parallel, the voltage increases to 400mV.
If I make the pin an input, the voltage goes up to 3.3V as expected.
If I make the pin full duplex standard USART1 TX with PP pin, the voltage goes to 3.3V.
I have removed all other components so it is just the processor pin itself, setting Open Drain just fails to give me a proper open drain, it seems to have something else loading the line.
Both pullup and pulldown resistors are disabled.
The initialisation for the port is from MX cube.
Is there a known issue with Open Drain on this version of processor?
If not, how should I initialise the port to get a real Open Drain output where the 4k7 pulls up to 3.3V.
Neither MX Cube or Claude seem to know?
