What is COM?

In the field of consumer PCs and notebooks the RS-232 port has been replaced by the USB. Nonetheless it still plays a big role for our customers in the industrial and POS sector. In this article we want to explain what stands behind this serial interface.

Serial and parallel ports

Serial ports, as well as  parallel ports serve the transmission of data between computers and peripheral devices. The first is called “serial” because the bits are being transmitted in sequence during this process.

As the name already tells, parallel ports transmit the bits parallel, so multiple bits at a time. The term of the parallel port has become associated with the IEEE 1284 port that is also known as the printer port.

The RS-232 or COM port

Talking about the serial interfaces of a (Mini-) PC, what is meant by this most of the times is the RS-232, better known as the COM port. RS-232 was already developed in 1960 for the telecommunication and IT field. Due to its easy implementation and its reliability, the interface was also used in the entertainment electronics. In 1997 the last update for the RS-232 specifications was released. For a long time PCs and laptops used the RS-232 to connect keypads and mice. By now, the USB port takes care of this task.

As usual for serial ports, the RS-232 transfers the bits in sequence via one single wire. For RS-232 this happens asynchronously and word wise. How this works is explained here.

The classic RS-232 interface is a 25-pin connector. Since the IT does not need every single one of these signals, the 9-pin connector was established (see image 1). If there is more than one COM port on a housing, the BIOS and the operating system give the physical ports a logical name, COM 1, COM 2 and so on (see image 1).

Data transfer rates of RS-232

As we know it from other cables, for instance HDMI, the data transfer rates depend on – among others – the length of the cable. For the RS-232 standard a maximum capacity, instead of a maximum cable length, is specified. These 2500 pF are reached with a length of 15 meters. There are also cables that show a very low capacity, with which up to 45 meters can be reached.

The RS-232 in times of Industry 4.0

Even today in the era of Industry 4.0 there are so many technical devices in the industrial sector that don’t survive without a serial interface. The RS-232 wins in this field with its functionality, which can be implemented easily and inexpensively, and because the interface is supported by most manufacturers and users.

In contrast to the Universal Serial Bus (USB), RS-232 doesn’t need a special driver for the applied operating system when used as the communication port. This leads to less support effort and to the security against system failures due to possible errors in the programming of the driver. Practice issues with the COM port are very rare. But if there is a problem, it is possible to simply exchange the hardware without touching the sensitive software.

Security overall plays a huge role in the industrial field. COM can score here, too: By using screwable cables, COM protects against dust and moisture in production halls, which also improves the health and increases the lifespan of a Mini-PC.

Differences between RS-232, RS-422 and RS-485

Next to the COM port there are other serial interfaces that have a place in some of our Mini-PCs. On one hand there is the RS-422 standard, also known as EIA-422 and on the other hand there is the RS-485 or EIA-485 standard.

The RS-422 standard stands for a grid-bound differential and serial data transmission. In contrast to RS-232 with unsymmetrical signaling, RS-422 requires a symmetrical signaling.

The RS-485 stands, just like RS-232, for an asynchronous serial, but also just like RS-422 for a symmetrical data transmission.

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18 Sep 2018 Array ( [id] => 344 [title] => What is LAN? [authorId] => [active] => 1 [shortDescription] => The abbreviations LAN or WLAN are probably known by anyone – no matter if you have heard it at home or at work. In this article we want to explain you what exactly stands behind LAN and what Ethernet and WOL have to do with it. [description] =>

Why do I need LAN?

The acronym LAN stands for Local Area Network and describes a computer network within a limited area. If you – for instance – connect one of our Mini-PCs with a network using a LAN cable, the PC can communicate with other devices to get access to the same server, use a printer or even an internet connection. You can also connect multiple Mini-PCs with one and the same router– it just means that they are using the same computer network.

The LAN or Ethernet cable RJ-45

To connect our Mini-PCs with the network, you simply need two things: The first one is the LAN interface on the PC itself and the second is a fitting LAN cable. Good news: All of our spo-comm Mini-PCs are equipped with at least one LAN interface.

The LAN cable, which is also called Ethernet cable, has a RJ plug connection. The RJ in this means Registered Jack and it stands for a standardized telecommunication network interface. This standard describes the construction of the sockets and plugs, as well as their contact assignment. The RJ-45 has an 8P8C assignment: This means that it has eight possible contact positions (P) and eight of them are in fact used (C). For this type there are cable in the categories 5/5e to 6e.

From LAN to Wireless LAN

For some of our spo-comm Mini-PCs you don’t necessarily need a LAN connection to connect it with other devices. A few of our PCs can be connected with devices by using the integrated or optional Wi-Fi. Wi-Fi which actually stands for Wireless Local Area Network (WLAN) is just a connection within a computer network that doesn’t need any cables.

Wake on LAN – WOL

The short-term WOL stands for Wake on LAN and is a standard by AMD that makes it possible to start a switched-off computer with the integrated network card. The requirement the PC has to offer is that the network card is still powered even when the PC is turned off. This requirement, by the way, is fulfilled by every single one of our Mini-PCs.

LAN expansion cards

There are, as well, special LAN extension cards which are not onboard as standard. These cards are needed if you want to increase the amount of the PC’s LAN interfaces. This can be advantageous if one and the same Mini-PC has to access multiple networks or devices, such as IP based surveillance cameras, at once. For our Mini-PCs of the BRICK series and two of the RUGGED-PCs, the spo-book RUGGED Q170 and the spo-book RUGGED GTX 1050Ti, there is a special adapter plate. For our spo-book NOVA CUBE Q87 there is a PCI expansion card.

If you have any questions about LAN, WiFi or Wake on LAN on your spo-comm device, feel free to contact us by mail.

##Explore all spo-comm Mini-PCs!

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know-how
What is LAN?
The abbreviations LAN or WLAN are probably known by anyone – no matter if you have heard it at home or at work. In this article we want to explain you what exactly stands behind LAN and what Ethernet and WOL have to do with it.
27 Sep 2018 Array ( [id] => 346 [title] => What is USB? [authorId] => [active] => 1 [shortDescription] => Two weeks ago we initiated our new series about interfaces on our spo-comm blog with the “What is LAN?” article. Today we want to continue the series with the commonplace USB port. We use it to charge our phones or to connect a mouse or USB-stick with our computer. In this article we want to give you a glimpse of what stands behind the well-known USB and what the differences between the various specifications such as USB 2.0 or USB 3.0 Gen. 2 are. [description] =>

Universal Serial Bus – USB

The short term USB stands for Universal Serial Bus and a serial communication that was developed by a merger of some companies – NEC and Microsoft for instance – to connect peripheral devices with a PC. A computer with a USB port, but also USB sticks can be connected at any time during system operation. In this process called Hot Swapping the external device and its features are automatically recognized.

From USB 1.0 to USB 3.1 SuperSpeed – The development of the interface

1996 was the year the first specification USB 1.0 with a data rate of 12 Mbit/s was released. With the introduction of USB 2.0 in 2000 even hard disks and video devices could be connected – thanks to the data rate of 480 Mbit/s.

Ten years ago the specifications of USB 3.0 SuperSpeed – also called USB 3.1 Gen 1 – with a data rate of 5 Gbit/s were presented. At the same time new cables and connectors were introduced. 2013 USB 3.1 – called USB 3.1 Gen 2 – was finalized and doubled up the speed of the predecessor to 10 Gbit/s. The latest specification USB 3.2 was released in 2017 and comes with a data rate of up to 20 Gbit/s.

By the way: ll spo-comm Mini-PCs are equipped with at least one USB 3.0 port!

USB transmission technologies

Using a host controller which is regularly based on the mainboard, the communication of USB can be managed. Only this host can read a devices’ information or send data to the device. The device can only send information if the host sends a query.
There are four established standards, which the USB controller chips hold on to and which are different in their performance and the implementation of features:

  • Universal Host Controller Interface (UHCI): Specified in 1995 by Intel with a data rate from 1,5 to 12 Mbit/s.
  • Open Host Controller Interface (OHCI): Developed by a consortium of companies and just marginal faster than UHCI.
  • Enhanced Host Controller Interface (EHCI): Provides USB 2.0 features and is designed for Hi-Speed mode (480 Mbit/s). For transfer to a USB 1.0/1.1 device OHCI and UHCI has to be supported.
  • Extensible Host Controller Interface (xHCI) : xHCI was released by Intel, provides USB 3.1 features and supports the SuperSpeed mode with 4 Gbit/s – with USB 3.1 even 9,7 Gbit/s.

The different plug types of USB

The Universal Serial Bus knows various plugs and connectors that differ in their measurements, but also in the possible data transmission speed.
The latest one is the universal USB Type C port, which is installed in many smartphones because of its low height and width. With this port data rates of up to 10 Gbit/s are possible, because USB 3.1 Gen 2 is supported. The USBC interface is suitable for transferring audio and video data parallel to USB data and supports DisplayPort, PCIe and Thunderbolt.

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##Read the “What is LAN?” article

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know-how
What is USB?
Two weeks ago we initiated our new series about interfaces on our spo-comm blog with the “What is LAN?” article. Today we want to continue the series with the commonplace USB port. We use it to charge our phones or to connect a mouse or USB-stick with our computer. In this article we want to give you a glimpse of what stands behind the well-known USB and what the differences between the various specifications such as USB 2.0 or USB 3.0 Gen. 2 are.
23 Oct 2018 Array ( [id] => 350 [title] => What is SPDIF? [authorId] => [active] => 1 [shortDescription] => Today we are sharing an article, in which we want to tell you about the interface SPDIF. Although it is mostly used in the consumer electronics field, some of our Mini-PCs are equipped with this port. In this article you will find what defines SPDIF, what it is used for and how it does compared to HDMI. [description] =>

SPDIF – Digital audio transmission: All in one

The short-term SPDIF, also S/PDIF, stands for “Sony/ Philips Digital Interface”. Behind this serial interface are the companies Sony and Philips who created SPDIF as a specification for transferring digital stereo and audio signals. Special about this is that SPDIF is able to transfer either optically or also electrically. The port is mainly used for CD players, between DVD players and in home cinemas, because harness can be avoided by using SPDIF.

Plug connections for SPDIF

Just like every other interface, SPDIF has special connectors, too. Within these it is differed between electrical plugs and plugs for optical transmission. For the latter the TOSLINK plug is used. The electrical transmission counts on an RCA plug with coaxial cable, very rarely also a 3.5 mm phone connector.

HDMI or SPDIF – How to transfer audio

HDMI as well as SPDIF are digitally transferring data, where HDMI is only electrical, SPDIF can even be constructed optically. In contrast to HDMI SPDIF is much older and therefore has one main disadvantage: At the beginning SPDIF was only built for PCM, by now the enormous bandwidths, for instance with DTS, are too big to be transmitted with SPDIF. A downmix of the data would be possible but would bring significant loss of performance. This is not the case by using HDMI. Another advantage of HDMI is that one cable can be saved because it transfers video and audio data at the same time.

spo-comm Mini-PCs with SPDIF:

•    spo-book WINDBOX III Evo

##See all spo-comm Mini-PCs!

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know-how
What is SPDIF?
Today we are sharing an article, in which we want to tell you about the interface SPDIF. Although it is mostly used in the consumer electronics field, some of our Mini-PCs are equipped with this port. In this article you will find what defines SPDIF, what it is used for and how it does compared to HDMI.