Browse Prior Art Database

USB Machine Control Panel

IP.com Disclosure Number: IPCOM000203739D
Original Publication Date: 2011-Jan-31
Included in the Prior Art Database: 2011-Jan-31
Document File: 4 page(s) / 159K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

In numerically controlled system in which the communication is realized by a field bus system a MCP (Machine Control Panel) is usually used as an interface between the operator and PLC (Programmable Logic Controller). A safe and real time communication between the MCP and the PLC has to be established. The communication between MCP and PLC is usually based on PROFIBUS (Process Field Bus) or some special transfer board. However, operators need to customize the MCP or use third party MCP. Therefore a novel solution for customizing the MCP is proposed. The MCP is designed as a vendor defined USB device and PLC as Universal Serial Bus (USB) host. MCP is enumerated as a Human Interface Device (HID) USB device with vendor defined usage page and usage ID. The proposed design is depicted in Figure 1. Furthermore, a monitoring mechanism is established by adding life sign in IN and OUT data transfer. Thus, the MCP and PLC can monitor each other.

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USB Machine Control Panel

In numerically controlled system in which the communication is realized by a field bus system a MCP

(Machine Control Panel) is usually used as an interface between the operator and PLC

(Programmable Logic Controller). A safe and real time communication between the MCP and the PLC

has to be established. The communication between MCP and PLC is usually based on PROFIBUS

(Process Field Bus) or some special transfer board. However, operators need to customize the MCP

or use third party MCP.

Therefore a novel solution for customizing the MCP is proposed. The MCP is designed as a vendor

defined USB device and PLC as Universal Serial Bus (USB) host. MCP is enumerated as a Human

Interface Device (HID) USB device with vendor defined usage page and usage ID. The proposed

design is depicted in Figure 1. Furthermore, a monitoring mechanism is established by adding life sign

in IN and OUT data transfer. Thus, the MCP and PLC can monitor each other.

The interrupt IN transfer is shown in Figure 2. The interrupt IN interval is described in the following:
1. The In token cycle should be less or equal than the PLC cycle.
2. The MCP acknowledges IN token with data (keys filter result) and the new MCP life sign (MCP

life sign increase 1 every time) for every coming IN token.
3. The PLC monitor the life sign of the MCP in every PLC cycle simplified by checking if the life

sign has increased (at least 1) compared to the last PLC cycle. If PLC finds the MCP life sign

has not increased for, e.g., 5 PLC cycles, the PLC reports a MCP error.

The precondition for the Interrupt OUT transfer is that the life sign of the PLC increases about 1 in

every PLC cycle.

The Interrupt Out interval is described in the following:
1. The OUT cycle should be less or equal than the PLC cycle. Otherwise MCP will lose PLC

data. If the OUT cycle is less or equal than the PLC cycle, there can be two cases for the host

to send the OUT data, see Figure 3.
2. MCP acknowledges mechanism: MCP acknowledges with ACK token when OUT data has

been received successfully.
3. MCP monitors PLC LS mechanism: The MCP has to set a timer to monitor the life sign of the

PLC. When the time of the timer is out and the life sign of the PLC stops increasing, the MCP

should report a host error. The timer can be set to, e.g., 5 times of PLC cycle.

The workflow of the proposed solution is shown in Figure 4.

The proposed solution is advantageous for the Firmware Update, since the USB connecter can also

be used as a boot loader. Thus, the customer can update the Firmware in the field. Compared with

boot loader using the interfaces RS232 or I2C, no additional boot loader pins on the MCP and the

special boot loader board is needed. The proposed solution is flexible, since the USB device has the

unique fea...