M
Hi,
I am a beginner in Python (FYI) and trying to communicate with the Gefran 800P programmer/controller using minimal Modbus library (Python + Mac). I am using USB to RS485 Serial Converter Cable (http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_USB_RS485_CABLES.pdf) to communicate with the Gefran device. Pins from the rear of the device (15+17 (Rx+Tx) & 16+18 (Gnd+Gnd)) are connected to Data +(A) and Data -(B) of the converter cable, respectively (RS485 - 2wired connection). I don't know the slave address for this device and there is no where mentioned about the address in the manual (http://www.primusthai.com/marketing/Gefran 800 (Controller).pdf).
I have tried:
Changing address of the slave form 0 to 247 and I always get the same message.
Tried checking for different register address and played around with function codes (3&4)
Played around with the programmer settings making sure both parameters in the code and the device are the same.
Nothing works!
Maybe I am missing something. Looking forward for your help. I am really stuck at this point for more than a week now!
When I run it, it gives me an error "ValueError: Too short Modbus RTU response (minimum length 4 bytes). Response: '\x00' ".
I enabled the local echo setting in the FTDI chip in the converter cable and I got a new error "ValueError: Checksum error in rtu mode: '\x00\xff' instead of '$\x00' . The response is: '\x00\x00\x00\x00\x00\x00\xff' (plain response: '\x00\x00\x00\x00\x00\x00\xff')
but if I run my code again, I get the old error (Too short modbus RTU...) back!
Looking forward for the help!
Regards,
Manasi
I am a beginner in Python (FYI) and trying to communicate with the Gefran 800P programmer/controller using minimal Modbus library (Python + Mac). I am using USB to RS485 Serial Converter Cable (http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_USB_RS485_CABLES.pdf) to communicate with the Gefran device. Pins from the rear of the device (15+17 (Rx+Tx) & 16+18 (Gnd+Gnd)) are connected to Data +(A) and Data -(B) of the converter cable, respectively (RS485 - 2wired connection). I don't know the slave address for this device and there is no where mentioned about the address in the manual (http://www.primusthai.com/marketing/Gefran 800 (Controller).pdf).
I have tried:
Changing address of the slave form 0 to 247 and I always get the same message.
Tried checking for different register address and played around with function codes (3&4)
Played around with the programmer settings making sure both parameters in the code and the device are the same.
Nothing works!
Maybe I am missing something. Looking forward for your help. I am really stuck at this point for more than a week now!
When I run it, it gives me an error "ValueError: Too short Modbus RTU response (minimum length 4 bytes). Response: '\x00' ".
I enabled the local echo setting in the FTDI chip in the converter cable and I got a new error "ValueError: Checksum error in rtu mode: '\x00\xff' instead of '$\x00' . The response is: '\x00\x00\x00\x00\x00\x00\xff' (plain response: '\x00\x00\x00\x00\x00\x00\xff')
but if I run my code again, I get the old error (Too short modbus RTU...) back!
Looking forward for the help!
Regards,
Manasi