As part of my student project I'm trying to establish a communication between the DataTaker DT85 and Swegon modbus gateway connected to CASA
ventilation unit (this is the first time I'm working both with modbus protocol and DataTaker). The aim is to have the values measured by the sensors in the unit also logged by the data logger. However, I receive the error E124.

The slave device is powered, I've previously checked the cabling and the communication between two units is done by RS485 connection, not TCP/IP. Below is the modbus code used while programming the data logger:

' User defined
'Sets up the DT85 serial sensor post
PROFILE "SERSEN_PORT" "MODE"="RS485"
PROFILE "SERSEN_PORT" "FUNCTION"="MODBUS_MASTER"
PROFILE "MODBUS_SERVER" "SERSEN_ADDRESS"="13"
PROFILE "SERSEN_PORT" "BPS"="19200"
PROFILE "SERSEN_PORT" "DATA_BITS"="8"
PROFILE "SERSEN_PORT" "STOP_BITS"="1"
PROFILE "SERSEN_PORT" "PARITY"="NONE"
PROFILE "SERSEN_PORT" "FLOW"="NONE"

RA1S 'Sample once per second

'Temperatures
1MODBUS(AD13,R3:0333,0.1)'Temp. 1 with scaling, deg C
1MODBUS(AD13,R3:0334,0.1)'Temp. 2 with scaling, deg C
1MODBUS(AD13,R3:0335,0.1)'Temp. 3 with scaling, deg C
1MODBUS(AD13,R3:0336,0.1)'Temp. 4 with scaling, deg C
1MODBUS(AD13,R3:0337,0.1)'Temp. 5 with scaling, deg C
1MODBUS(AD13,R3:0338,0.1)'Temp. 6 with scaling, deg C
1MODBUS(AD13,R3:0339,0.1)'Temp. 7 with scaling, deg C
1MODBUS(AD13,R3:0340,0.1)'Temp. 8 with scaling, deg C

'Measurements
1MODBUS(AD13,R3:0342,0.1)'CO2, ppm
1MODBUS(AD13,R3:0342,0.1)'RH%, %
1MODBUS(AD13,R3:0342,0.1)'Pressure 1, Pa
1MODBUS(AD13,R3:0342,0.1)'Pressure 2, Pa
1MODBUS(AD13,R3:0342,0.1)'Fan control input, 1-5

What may be the possible reason the transaction fails?

Hi KatarzynaLuc,

When you set dataTaker as MODBUS Master, you do not need to set its slave address.

PROFILE "MODBUS_SERVER" "SERSEN_ADDRESS"="13"
The above profile setting will be used only if you set dataTaker as MODBUS slave.

E124 error message might related to unknown address as I assumed you use dataTaker slave address to read CASA ventilation unit.
Swegon MODBUS gateway has its own setting of slave number and baudrate.

Bus speed can be set using baudrate dip switch (19200 will have DIP1=0 and DIP2=1), while unit address can be set using address dip switch (address 1 will have DIP1=1 and DIP2-DIP8=0).

Check the attachment:

If you use address 1 on your gateway, you need to modify your program to read address 1.

Best regards,
Rudy Gunawan

Thank you for the quick answer.

I've removed the line responsible for setting the slave address and changed the address in the code to 1 ("AD1"). Still, I receive the same error. The setup of the Swegon modbus gateway is as shown in the attached photo:

'Sets up the DT85 serial sensor post
PROFILE "SERSEN_PORT" "MODE"="RS485"
PROFILE "SERSEN_PORT" "FUNCTION"="MODBUS_MASTER"
PROFILE "SERSEN_PORT" "BPS"="19200"
PROFILE "SERSEN_PORT" "DATA_BITS"="8"
PROFILE "SERSEN_PORT" "STOP_BITS"="1"
PROFILE "SERSEN_PORT" "PARITY"="NONE"
PROFILE "SERSEN_PORT" "FLOW"="NONE"

RA1S 'Sample once per second

'Temperatures
1MODBUS(AD1,R3:0333,0.1)'Temp. 1 with scaling, deg C
1MODBUS(AD1,R3:0334,0.1)'Temp. 2 with scaling, deg C
1MODBUS(AD1,R3:0335,0.1)'Temp. 3 with scaling, deg C
1MODBUS(AD1,R3:0336,0.1)'Temp. 4 with scaling, deg C
1MODBUS(AD1,R3:0337,0.1)'Temp. 5 with scaling, deg C
1MODBUS(AD1,R3:0338,0.1)'Temp. 6 with scaling, deg C
1MODBUS(AD1,R3:0339,0.1)'Temp. 7 with scaling, deg C
1MODBUS(AD1,R3:0340,0.1)'Temp. 8 with scaling, deg C

'Other measurements
1MODBUS(AD1,R3:0342,0.1)'CO2, ppm
1MODBUS(AD1,R3:0342,0.1)'RH%, %
1MODBUS(AD1,R3:0342,0.1)'Pressure 1, Pa
1MODBUS(AD1,R3:0342,0.1)'Pressure 2, Pa
1MODBUS(AD1,R3:0342,0.1)'Fan control input, 1-5

Hi Katarzyna,

Other than address, you may need to check the corresponding register type.

I found CASA MODBUS manual (see the attachment).
According to the manual address 300+ is only available for holding register (register type 4 – write/ read).

Please use type 4:
1MODBUS(AD1,R4:0333,0.1)'Temp. 1 with scaling, deg C

Prior to another trial you may need as well activate MODBUS diagnostic mode (P56=4).
Then send one line of code to test the response from the logger.

If you still see E124 error, please send more lines to the logger then email me those response for further review.

Notes:
If this is not the MODBUS manual that you currently have. Could you please send me yours?

Best regards,
Rudy Gunawan

Hi Rudy,

Changing the registers to 4 didn't help, also - according to the modbus manual for the CASA units there are no commands in register 4 that correspond to what I would like to do. The list of registers I've been using is in the attachement.

Below is the current code (with register 3) and the response from the logger:

Code:
'Sets up the DT85 serial sensor post
PROFILE "SERSEN_PORT" "MODE"="RS485"
PROFILE "SERSEN_PORT" "FUNCTION"="MODBUS_MASTER"
PROFILE "SERSEN_PORT" "BPS"="19200"
PROFILE "SERSEN_PORT" "DATA_BITS"="8"
PROFILE "SERSEN_PORT" "STOP_BITS"="1"
PROFILE "SERSEN_PORT" "PARITY"="NONE"
PROFILE "SERSEN_PORT" "FLOW"="NONE"

RA1S 'Sample once per second

'Temperatures
1MODBUS(AD1,R3:0333,0.1)'Temp. 1 with scaling, deg C 1MODBUS(AD1,R3:0334,0.1)'Temp. 2 with scaling, deg C 1MODBUS(AD1,R3:0335,0.1)'Temp. 3 with scaling, deg C 1MODBUS(AD1,R3:0336,0.1)'Temp. 4 with scaling, deg C 1MODBUS(AD1,R3:0337,0.1)'Temp. 5 with scaling, deg C 1MODBUS(AD1,R3:0338,0.1)'Temp. 6 with scaling, deg C 1MODBUS(AD1,R3:0339,0.1)'Temp. 7 with scaling, deg C 1MODBUS(AD1,R3:0340,0.1)'Temp. 8 with scaling, deg C

'Measurements
1MODBUS(AD1,R3:0342,0.1)'CO2, ppm
1MODBUS(AD1,R3:0342,0.1)'RH%, %
1MODBUS(AD1,R3:0342,0.1)'Pressure 1, Pa
1MODBUS(AD1,R3:0342,0.1)'Pressure 2, Pa
1MODBUS(AD1,R3:0342,0.1)'Fan control input, 1-5

Response:
DT85> P56=4
DT85> Modbus TX >SS: 01 04014c0001f1e1 (8)
Modbus timeout
dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04014d0001a021 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04014e00015021 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04014f000101e1 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04015000013027 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 040151000161e7 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 040152000191e7 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 0401530001c027 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04015500012026 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04015500012026 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04015500012026 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04015500012026 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed Modbus TX >SS: 01 04015500012026 (8) Modbus timeout dataTaker 85 E124 - Modbus transaction failed
1+Temp. UnderRange degC
1# Temp. UnderRange degC
2+ Temp. OverRange degC
2# Temp OverRange degC
3+ Temp. OverRange degC
3# Temp. OverRange degC
4+ Temp. OverRange degC
4# Temp. OverRange degC
5+ HMW83 (1) Temp. -5.0 degC
5# HMW83 (1) RH 0.0 % H2O
6+ HMW83 (2) Temp. -5.0 degC
6# HMW83 (2) RH 0.0 % H2O
7+ HMW83 (3) Temp. -5.0 degC
7# HMW83 (3) RH 0.0 % H2O
8+ HMW83 (4) Temp. -5.0 degC
8# HMW83 (4) RH 0.0 % H2O
9+ HMD53 (1) Temp. -40.0 degC
9# HMD53 (1) RH 0.0 % H2O
10+ HMD53 (2) Temp. -40.0 degC
10# HMD53 (2) RH 0.0 % H2O
11+ HMD53 (3) Temp. -40.0 degC
11# HMD53 (3) RH 0.0 % H2O
12+ HMD53 (4) Temp. -40.0 degC
12# HMD53 (4) RH 0.0 % H2O
13+ HMT130 (1) Temp. -40.0 degC
13# HMT130 (1) RH 0.0 % H2O
14+ CO2 (1) 0.1 PPM
14#CO2_1 0.1 PPM
4C Oil meter 0 Counts
Electricity meter 3 0 Counts
4D Electricity meter 0 Counts
1C Flow meter (1) 0 Counts
2C Flow Meter(2) 0 Counts
3C Flow Meter (3) 0 Counts
Actual oil cons. 0.0 Liter
Energy cons. water 2 OverRange kWh
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet
1MODBUS NotYetSet

Best regards,
Katarzyna

Hi Katarzyna,

There is no response at all from CASA gateway.
There are several cause for this event:

• sensor needs a repeat request or more time out (you may add RT3 to enable 3x retries and TO5 to wait for 5 second). 1MODBUS(AD1,R3:0333,0.1,RT3,TO5)
• incorrect wiring
• incorrect device setting
• incorrect port setting

Could you give me your wiring detail between CASA Modbus Gate and dataTaker?
Port A should be connected to TxZ, port B to RTS Y and GND to D GND.

Although it rarely happen, you may try to swap between red and purple wire if the above setting does not work.

What is the length of your RS485 cable and your setting for bus termination?
Sometimes it is important to add termination resistor in order to strengthen the signal.

Other possible solution may come from data bits and stop bit setting.
This is also a very rare occurrence, I have experience in one device having 8N2 setting.

Notes:
You do not need to enter the whole program for checking MODBUS response.
Using one line of code from command interface while enabled MODBUS diagnostic is enough.

Best regards,
Rudy Gunawan

Hi Rudy,

Swapping the cables solved the problem (I reconnected A to RTS Y and B to
TxZ) and it seems to be reading and logging the measurements from the sensors in the unit just fine.
Thank you very much for all the help.

Best regards,
Katarzyna Luc