Running DIO VTS 1.1 from 3 June with b115 of dio implementation on RPI found that tests:
api/jdk/dio/adc/ADCChannelConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/atcmd/ATDeviceConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/counter/PulseCounterConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/dac/DACChannelConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/generic/GenericDeviceConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/gpio/GPIOPinConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/gpio/GPIOPortConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/i2cbus/I2CDeviceConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/pwm/PWMChannelConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/spibus/SPIDeviceConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/uart/UARTConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]
api/jdk/dio/watchdog/WatchdogTimerConfig/index.html#S11n[testSerializeNull,testSerializeReturnValue,testS11nGeneral]

fail with following output:
"testSerializeNull: Failed. serialize(null): NPE is expected, IOE is thrown
testSerializeReturnValue: Failed. serialize(okay): IOE is thrown
testS11nGeneral: Failed. serialize(okay): IOE is thrown"

Please find attached used configuration file and jtr example.