Strange issues with RS485 Communications

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Jameson
Posts: 860
Joined: Fri Nov 04, 2011 7:42 pm
Location: Santa Cruz, CA
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Re: Strange issues with RS485 Communications

Post by Jameson »

Hello Alfonso,

I have seen very similar data to this. The data you are showing is quite garbled.

The first thing I look at is, are my serial settings correct? Do you have your serial port set to 9600 baud, 7 data bits, even parity, and no flow control? Now that I look at your screenshot again it looks like you do have this.

The second questions would be, what type of communication converter are you using? Is it one of ours? If you use incorrect biasing resistors you can get data that looks like this (a bunch of 20s rather than a bunch of 30s, 99% of the response should be bytes that start with a 3: 31, 32, 33 etc.)

Do you have more than one meter connected to the RS485 bus? If you do, you will need to format the meter request with the meter number included. You are sending a request to meter number 999999999999 (12 9s is the default address) this will only work if one meter is connected. If you have more than one meter connected, all of the meters will respond at the same time, and flood the RS485 bus. This will look like garbled data. What is your meter number? I can help you format the meter request if you would like.

Are you able to read your meters with our EKM Dash software? If you can, you can use the "Hex Inspector" to sniff the serial traffic.

Please let us know if you have any questions.
Jameson
EKM METERING
http://www.ekmmetering.com
831.425.7371
Jameson
Posts: 860
Joined: Fri Nov 04, 2011 7:42 pm
Location: Santa Cruz, CA
Contact:

Re: Strange issues with RS485 Communications

Post by Jameson »

I'm using an FTDI based usb->RS485 converter.
It is good that you are using the FTDI chip. We have found FTDI to be far superior. We use this in our USB to RS485 converter:

http://www.ekmmetering.com/ekm-metering ... erter.html

Bad news is you are using an unknown converter, this has caused us headaches in the past. We try to help someone for a while and it turns out they are not using our USB converter. All FTDI USB converters are not made alike.

One of the problems that we did have with it is that the biasing resistors were the wrong value. We we really recommend our USB Converter as it uses 470ohm biasing resistors. I would strongly suspect that this could be the source of your issue. Not trying to sell you a converter, just trying to make it easier on everyone.

Are you able to solder? I could help you if you want to try and solder 470ohm biasing resistors onto your own converter.

Let me know if you have any questions.
Jameson
EKM METERING
http://www.ekmmetering.com
831.425.7371
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