## 4 Hardware Architecture
### 5G Module Interface and Time Synchronization  
The connection between the 5G module and the microcontroller is external. Thus, it requires specific design attention concerning water-proof connections needed for machine-integrated applications in connection with coolant. Time synchronization is essential for the MSP, as the ultimate goal is to aggregate data within the trial site in real time. Because the synchronization features of 5G were still under development at the time of the project, the chosen component is the _u-blox(tm) SARA-R5_ (Thalwil, Switzerland), a 4G LTE component that is a module for Industrial Internet of Things (IIoT) solutions due to its characteristics such as security, wide coverage, and compatibility with other _u-blox(tm)_ families. Moreover, it has low power consumption, long battery life, and low costs.  
The serial communication interfaces of the module are universal asynchronous receiver-transmitter (UART) and USB. A microUSB-B interface is needed to implement the device's diagnostics. A network indicator with a green LED allows for verification of the network status. A micro-SIM connector links the _u-blox(tm) SARA-R5_ with the external SIM.  
An external DC power supply is required for the radio module. In order to minimize the system power consumption when it is not used, an ultra-low resistance load switch is inserted inside the board [18].  
For connectivity to the 5G module, a standard Ethernet interface and USB are provided. The Ethernet is preferred, as it has less IP overhead as compared to the USB. The 5G module used also has an Ethernet interface to transfer data between the controller and the module.  
The main elements of the Ethernet interface are Ethernet physical layer transceiver, signal transformer, and circuit protection.  
* The Ethernet physical layer transceiver is a _Micrel Inc.(tm) KSZ8081 RNB_ (San Jose, CA, USA). The role of this device is to provide a transceiver for data transfer and reception and to enable the Reduced Media Independent Interface(tm) (RMI) needed to reduce the number of data interfaces. It has a single power supply of 3.3 V. The connection between the Ethernet physical layer transceiver and the external ancillary module is provided by a connector. A magnetic interface is needed to realize the connection [19].
* The signal transformer is a _Pulse Electronics(tm) H1102_ (San Diego, CA, USA), which is needed to interface the ancillary module to the Ethernet physical layer transceiver using a magnetic surface port [20].
* The _STMicroelectronics(tm) USBLC64_ implements a protection circuit to prevent malfunctions of the device in the case of electrostatic discharges. It is realized by connecting the data transceiver with the ESD suppressor [21].  
The main components of the USB interface side are a USB-to-UART bridge controller, a digital isolator, and two micro-USB connectors, which make the microprocessor behave like a host. A step-up converter is needed to generate the 5 V for the microprocessor USB peripheral.  
* The USB-to-UART bridge controller is a _SiliconLabs(tm) CP2102N_ (Austin, TX, USA). The component manages the data exchange between the USB and the UART peripherals and integrates the connection with the microprocessor. The transmission data rate is up to 3 Mbaud, and the average operating current is 9.5 mA [22].
* The digital isolator is a _Texas Instruments(tm) ISO7221C_ (Dallas, TX, USA). The dual-channel isolator implements the translation of voltage during data transmission and reception. High voltages are filtered [23].