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MN4000/4100 Modbus Infomation

Home Technical Q&A MN4000/MN4100 MN4000/4100 Modbus Infomation
  1. MODBUS AND HTML

 

The MN4000 and MN4100 have Modbus TCP and HTML access for image display and analysis.

 

1.1 Modbus TCP

The Modbus protocol used is Modbus TCP/IP also known as Modbus TCP.

Following Modbus command function codes are used:

  • Function code 3: Read Multiple Registers
  • Function code 4: Read Input Registers
  • Function code 6: Write Single Registers
  • Function code 16: Write Multiple Registers 

Modbus TCP/IP connects over TCP/IP networks using port 502. A checksum is not required as a checksum calculation implemented in the lower layers already provides checksum protection. The frames do not include a checksum. 

12.1.1 Register Access: code 4

The AW implements Modbus TCP command function code 4 “Read Input Registers” (16 bit), with the addresses as defined in the following table.

 

Address* Function Code: 4 Comment
0 to 4799 Sensor temperature array, 80 x 60

Units: cK (centikelvin)

Global constants:

Emissivity=1

0=Top LHS, 4799=Bottom RHS

4800 AlarmBit[24:16] for each bit

1: alarmed

0: no alarm

Corresponds to the 25 temperature limit areas

Alarmed for any pixel>TSET

4801 AlarmBit[15:0] for each bit

1: alarmed

0: no alarm

Corresponds to the 25 temperature limit areas

Alarmed for any pixel>TSET

*Modbus access is big-endian

Table 12.1.1 Modbus Function code 4 TCP registers

12.1.2 Register Access: code 3, 6, 16

The AW implements Modbus TCP command function code 3, 6 and 16 with the addresses as defined in the following table.

 

Address* Function Code: 3, 6, 16 Comment
0 to 24 Sensor alarm array, 5 x 5

Units: cK (centikelvin)

0=Top LHS, 14=Bottom RHS

*Modbus access is big-endian

Table 12.1.2 Modbus Function code 3, 6, 16 TCP registers

1.2 HTML Browser

 

Web browser is used to setup all aspects of the camera operation.

 

HTTP browser access can be used to access camera data structures as follows:

http:IP-address/vis.jpg visible image jpeg
http:IP-address/ir.bmp IR image
http:IP-address/raw.bin IR temperature array, 80 x 60 x 16bit
http:IP-address/lep.bin IR info

 

http:IP-address/alarm.bin alarm settings, 5 x 5 x 16bit

 

 

 

1.2.1 Alarm Temperature Thresholds

 

Alarm temperature thresholds are setup via the Alarm window which overlays the alarm grid on the visible image

alarm

1.2.2 Browser – Location Identification

The browser home screen can be used to identify object coordinates.

The mouse location is given as a register within the displayed image. In this case register 3030 is the mouse location as shown below with a temperature of 21C.

The red and blue spot temperature indicators show maximum and minimum scene temperatures respectively.  

cam-pic

The image shows highlight mode which auto-sets the overlay temperature threshold providing a useful quick setup for displaying the scene hot spots.

1.3 Window Coordinate Conversions

For user co-ordinates the bottom LHS is considered to be location (x=0, y=0).

 

(0, 59)=0000 (79, 59)=0079
(0, 0)=4720 (79, 0)=4799

 

Figure 12.3 Pixel x, y coordinates

 

For a location within the scene area conversion to and from the Modbus register is as follows:     ModbusReg [x, y] = x + (59 – y)*80, for location (x, y)

Examples:

  • ModbusReg [0, 0] = 0 + (59 – 0)*80 = 4720
  • ModbusReg [79, 0] = 79 + (59 – 0)*80 = 4799
  • ModbusReg [0, 59] = 0 + (59 – 59)*80 = 0000
  • ModbusReg [79, 59] = 79 + (59 – 59)*80 = 0079

To get the (x, y) coordinates from the ModbusReg  Y-coordinate:

  • Y-coordinate [ModbusReg] = abs( ModbusReg / 80 ) = the number of times 80 subtracts from ModbusReg  To convert to Cartesian as in diagram subtract 59 from this number

X-coordinate

  • X-coordinate [ModbusReg] = remainder after subtraction used to obtain the Y-coordinate

 

 

 

 

 

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