Raspberry Pi serial interfacing

The Raspberry Pi, the single-board computer that has been causing so much excitement lately, has actually got two serial ports. One is a “mini-uart” with interfacing built into the Raspberry Pi’s GPIO (General Purpose Input-Output) interface.

The GPIO interface is a pin header, and the relevant serial port pins are as shown:

Raspberry Pi mini UART GPIO pins

The Raspberry Pi Quick Start Guide from element 14 describes the process in simple terms:

Serial connection
The Serial Port is a simple and uncomplicated method to connect to the Raspberry Pi. The communication depends on byte wise data transmission, is easy to setup and is generally available even before boot time.

First interaction with the board
Connect the serial cable to the COM port in the Raspberry Pi, and connect the other end to the COM port or USB Serial Adapter in the computer.

Serial Parameters

The following parameters are needed to connect to the Raspberry. All parameters except Port_Name and Speed are default values and may not need to be set.
• Port_Name: Linux automatically assigns different names for different types of serial connectors. Choose your option:
Standard Serial Port: ttyS0 … ttySn
USB Serial Port Adapter: ttyUSB0 … ttyUSBn
• Speed: 115200
• Bits: 8
• Parity: None
• Stop Bits: 1
• Flow Control: None

The Serial Port is generally usable by the users in the group dialout. To add oneself to the group dialout the the following command needs to be executed with root privileges:
$useradd -G {dialout} your_name

The implementation of the serial port on the Raspberry Pi GPIO is not a full implementation; it has only the pins available on the pin header, for example (GND, TX, RX).

The second UART is a more fully implemented UART that is part of the internal ARM architecture of the Broadcom BCM2835 chip, the core of the Raspberry Pi. Details on this UART will be forthcoming in another blog post.

Atlas POS

Atlas POS, a POS integrator specializing in Sharp ECRs, operates throughout Canada from Vancouver to Newfoundland. They have now used LAVA Ether-Serial Links and HQ-ST Plus Links in numerous POS polling applications. They focus on POS installations for cafeterias, and have sold systems to colleges, universities, and hospitals, as well as to companies such as BMW and Rogers.

Norm Puig at Atlas sees increasing need for machines that require networking, either natively in the machine, or through IP-enabling technology such as the Ether-Serial Links and HQ-ST Links that he installs. His observation is that for installations where the requirement for complex cash registers is high, as when an organization has a large number of inventory items to manage, the ECRs and POS systems are Ethernet ready. By contrast, when the cash register requirements are simpler or stores are smaller, IP-enablers make more sense.

Sharp ER-A520

Typical installations for Norm include Ether-Serial Links for polling Sharp ER-A420 cash registers, polling with Skantalk software, at the Royal Conservatory, Toronto; HQ-ST Links polling Sharp UP600 registers in the Sweet Tooth Candy Emporium chain, and Sharp ER-A520 cash registers being connected with Ether-Serial Links in the Old Forum Inn, Cambridge, ON.

Norm prefers the ease of use he finds in the LAVA products to some of the more difficult to use products on the market.

Retail Solutions Providers Association

We’d like to devote this blog post to promoting the RSPA (Retail Solutions Providers Association), the major retail technology group (now over 60 years old). If you’re in the POS business we strongly suggest you consider joining.

The RSPA is an invaluable source for networking and information, and an active participant in promoting understanding of the PCI (Payment Card Industry Security Compliance), a very important industry  initiative to understand.

RSPA’s print publication Connect, email newsletter jiuce-news, and web site gorspa.org are full of articles on emerging technologies, current industry events, legal topics, and much more. RSPA also hosts the RetailNOW and INSPIRE conferences and conventions, and makes a membership directory available to its members.

The benefits of membership are a no-brainer for many — the membership cost is often more than offset by savings from services and affinity programs such as those below:

• The RSPA Legal Assistance Program offers a Legal Hotline (no-cost legal consultation),
contracts and forms packages, strategic partner packages, and employment packages
to help you run your business.

• RSPA has joined with Sentry Insurance to offer a new Property and Casualty
Protection Plan at group rates for RSPA Members.

• Educational seminars for all levels of retail technology professionals are
offered at both of RSPA’s summer and winter events, RetailNOW and INSPIRE,
as well as through other newly released programs.

• RSPA awards over $100,000 in college scholarships each year. Children,
grandchildren, full-time employees, and children of full-time employees of an
RSPA reseller member are eligible for an RSPA scholarship.

• Affinity programs for RSPA members — with special rates and pricing for services
and products — are available through UPS, Fedex, Nashua, Office Max, Sprint, and others.

Full details on the RSPA can be found at www. gorspa.org.

Customized Parallel-PCI

LAVA’s Parallel-PCI card is well-regarded for its speed and compatibility in many systems and applications, but every so often someone needs something special. In the case of Lockheed Martin, as they were developing a system for the US Postal Service they uncovered the need for a parallel port card that delivered a particular output voltage on its pins.

The modification LAVA produced met a real-world requirement for improvements in the parcel-handling systems of the US Postal Service — the conveyer equipment needed this particular parallel port voltage to operate properly. Not every supplier of cards is the manufacturer, and not every manufacturer is able and willing to make customized versions of stock products to meet a particular customer’s requirements. LAVA, with all functions from design, through manufacturing, to post-sales support, can do the job.

Lockheed Martin Parallel-PCI