USB provides universal industrial HMI solution

Bruce Piggot of CKS explains that working with the right partner brought USB solutions to industrial keyboard and trackerball applications.

Bruce Piggot of CKS explains that working with the right partner brought USB solutions to industrial keyboard and trackerball applications.

Since its inception in 1996, the USB (Universal Serial Bus) has become the industry standard for PC connectivity.

It brings a number of significant advantages to all computing platforms: it is a true plug-and-play standard; it eliminates the need for multiple I/O standards; and it reduces overall system cost.

USB is the efficient, standardised PC interface for peripheral devices, enabling all devices to have the same connector and to be automatically recognised by the PC.

The system offers extra flexibility since it is not necessary to plug a particular device into a specific USB connector.

Up to 127 peripheral devices can be connected to one PC using dedicated hubs or devices with hub functionality.

Consequently, several devices, including devices of the same type, can work in parallel on the same machine, leaving the remaining I/O ports free for other uses.

USB is a greener interface that has the ability to shut down devices that are not being used.

Other benefits include the facility to hot plug devices.

The USB connector is much more durable than standard PS2/AT connectors as there are no exposed pins, and USB keyboards can be connected to other non PC systems, such as Apple Mac.

CKS Holdings is a UK-based worldwide manufacturer of HMI products that include keyboards and trackerballs, local operator interface input devices, displays and industrial computers.

All CKS products are sealed to a minimum of IP54, and are designed for the harshest industrial environments possible.

After reviewing available devices, CKS chose US-based Cypress Semiconductor which manufactures a range of microprocessors for the implementation of USB/PS2 keyboards and mice.

With headquarters throughout Europe and the far east, Cypress has to date, shipped nearly 200 million USB devices, all robust and reliable enough for any USB application.

To enable it to add a USB keyboard to its range of standard 128-key industrial sealed keyboards, CKS used a Cypress microprocessor as replacement for the existing Atmel 89C81/2 variant.

The Cypress USB peripheral controller has a built-in USB interface engine that is important for two reasons.

It controls the power management requirements of the USB specification.

And it performs all the high-speed communications independently of the main processor, even when the microprocessor is in sleep mode.

The Cypress microprocessors were also lower cost than the original units and have more I/O pins.

The extra I/O is achieved because there is no reset line - all reset functions are internal.

Also, there is no required external reset line which gives an effective 34 I/O lines (including the USB/PS2 lines).

This allows a single chip keyboard design with an 18 x 8 (144 key) keyboard matrix, three LED drive, one beeper drive and two auxiliary lines for a second communication channel such as a PS2 mouse input, without any extra support circuits.

"It wasn't just a case of picking each others brains", states Bruce Piggott, CKS USB Senior Development Engineer, "it was a case of two specialist, in their particular fields, combining to bring about a successful USB solution.

We worked closely with Cypress with their reference firmware which was made available to us".

In order to promote its range of USB microprocessors, Cypress commissioned the development of firmware to implement the standard range of PC keyboards and mice in both USB and PS2 formats.

This code for the combination keyboard and PS/2 mouse with a USB interface was offered to CKS so the company was able to use Cypress microprocessors for its future USB keyboards.

The code has been extended and modified by CKS to include key strings, multiple dupe key suppression, key beep and illegal key sequence trap.

As a bonus, the USB engine can also handle the PS/2 communication hardware interface, which gives a common solution to future keyboard requirements.

The Cypress microprocessor is supported by a low cost in circuit emulator, programmer and assemble/linker package.

The standard packaging is OTP (one time programmable).

The Cypress CY7C634xx USB peripheral controller family (M8T Series) are 8bit RISC one time programmable (OTP) microcontrollers.

The instruction set has been optimised specifically for USB and PS/2 operations, although the microcontrollers can be used for a variety of other embedded applications.

In the CKS application, the microcontroller also handles keyboard scanning and resolves the two-key rollover problem.

The USB protocol is simple for the end user but complex for the developer.

The ability to hot plug a wide range of peripheral devices into a PC and for these devices to be automatically recognised and configured carries a high price in USB device complexity.

To produce a USB interface from scratch would take a long time.

Cypress UK made available pretested code that could be modified to suit CKS requirements.

These modifications were assisted by a Cypress USB specialist (Rob Graham) who could advise on complex issues.

Cypress UK also gave access to USB analysis equipment and software tools that helped solve some difficult issues of compatibility.

This speeded development of a range of USB/PS2 keyboards and trackerballs by CKS.

Subsequent to the development phase many technical issues have been resolved by direct communication with Cypress UK.

To develop a USB/PS2 Trackerball, CKS once again worked with Cypress to produce the necessary firmware.

The Trackerball uses universal software that can automatically detect if it is connected to a USB or PS/2 port.

The USB protocol allows a large range of devices to have the same connector.

The system automatically determines which device is attached and loads the appropriate driver.

The new USB/PS2 Trackerball was developed, along with Cypress, in ultra-quick time and worked first time.

CKS based its development work on Cypress' newer Encore (enhanced component reduction) family of low-speed USB microcontrollers.

The Cypress Encoret Series offers: reduced system cost through external component integration; an integrated crystal-less oscillator; USB PS/2 auto-configuration with no external resisters required; integrated programmable memory for firmware storage and data buffering; internal wake-up and watchdog timers; and brownout detection and low-voltage reset.

Typical applications are all HMI devices including: mice, keyboards, barcode readers and front panel displays.

All CKS PS2 and USB Industrial sealed keyboards and trackerballs carry an exceptional 5-year warranty.

Back to top