I got it working now, but only after finding that there must be a mistake in either the Dev Board or the documentation:
In the docs is stated:
16.39. Uart Class Inherits Object:    Public Sub Create(baudRate As Integer, tx As Pin, rx As Pin)
But I found that Rx comes first and then Tx.
So this works fine: ser = Uart.Create(9600, Pin.Pin1, Pin.Pin0) // Pin 1 to Rxd and pin 0 to TxD; Dev-Board default jumper config 
Also something not working like it should:
ser.Write("Hello") ser.Write(0x0c) ser.Write(0x0a)    this seems to give a newline but no line feed, so my line is overwritten in Putty and disappears, I found out after putting in a loop for 50 times.
when I do the following:
ser.Write("Hello") ser.Write(13) ser.Write(10)       it works, how comes?