RS 485 Communciation Problem

Hi,

I'm currently trying to communciate a Remote 1104 particle counter with Keyence KV-L20R using a 2 wire RS485. I'm able to send data from KV-L20R to the 1104, but I am not able to receive data from the 1104 to KV-L20R.

I've tried using windows Hyperterminal to test the communication.

KV-L20R has no problem transmitting and receiving data from the Hyperterminal.

1104 also has no problem transmitting and receiving data from the Hyperterminal.

Any advice on why I'm not able to receive data from remote 1104 to KV-L20R will be appreicated.

Thanks!

I don't understand how you got it talk at all.

From the spec sheet on the web (I couldn't find a manual) for Lighthouse 1104:

http://www.golighthouse.com/products_aerosol_r1104.asp

Communication Modes:


RS 485 MODBUS, RS 485 MR

I don't know what RS-485 MR means.

But RS 85 Modbus means that the 1104 is a Modbus slave and that means you need to talk to it as a Modbus master, or it won't respond.

If you connected hyperterminal, you'd have to send a Modbus formatted data string that includes the correct CRC value to get a response. Did you do that?

If you didn't, how what exactly did you do that made you think the connection worked?

When I test Modbus devices I use an application called Modscan32. But without a lot of hand coding and a CRC calculator to create a proper Modbus formatted data string, I don't know how one would use Hyperterminal to talk Modbus.

Maybe that 'RS-485 MR' feature is some ASCII terminal response?

The serial port on a PC is RS-232, not RS-485.
Most PCs do not have RS-485, unless
- an options RS-485 comm card is added
- or an RS-232/485 converter is used

Which hardware are you using to get RS-485 functionality?

Dan

Hi Dan,

According to the manual, "MR Protocol allows the instrument to be controlled remotely from a third party application program, such as ProCOMM or WIndows Hyperterminal"

Yes, I believe MR Protocol is some ASCII terminal response.

Allow me to clarify myself further.

The KV20LR has 2 communciation mode, RS232 or RS485.

The 1104 has 1 communcation mode RS485

When I connect KV20LR to the hyperterminal, I'm using RS232 and there's no issue.

When I connect 1104 to the hyperterminal, I'm using a RS232-485 converter, there's also no issue.

When I connect 1104 to the KVL20R using either RS485 or using the RS232-485 converter, it's always the same issue of me able to send data to the 1104, but not able to recevie any data.

I'm not using the modbus protocol as KV20LR doesn't support it.Thus I need to use the MR Protocol as I control the 1104 via keyence PLC.

Thanks for the clarifictions.

Is the data you send to the analyxer accepted by the analyzer? Like setup parameters? Can you somehow check to see that the write from the Keyence actually is accepted by the analyzer?

What does the manual list as the kinds of data that the analyzer can send ? particle counts?

What sort of protocol is MR described as?

Does the analyzer need a request to send data?
Or does the analyzer broadcast a count on a timed interval?
Or does it wait for a token to talk, then pass the token to another analyzer?

Can the statement "MR Protocol allows the instrument to be controlled remotely from a third party application program, such as ProCOMM or WIndows Hyperterminal" mean that you can send it control parameters of some sort, but not necessarily read data back from the analyzer, because it sasy "controlled remotely" which might mean "analyzer accepts control parameters (whatever that means), not that the analyzer sends data.

DAn

Hi Dan,

The data send and received by the remote 1104 is ASCII characters.

I've checked with Keyence side and that there is no problem on the setup parameters.

The 1104 will wait for a pre-set ASCII character command before it will send the data in ASCII string form.

I am sure the 1104 is able to send data as I am able to receive data through the hyperterminal from the 1104.

review:
KV20LR: RS232 or 485
1104: RS485 only
PC: RS232 only

PC to KV20LR with HT (Hyperterminal) = OK
PC to 1104 with HT = no issue
PC to converter to 1104 = no issue

KV 20LR to 1104 via RS485 direct = send to 1104 OK, can't receive from 1104
KV20LR to 1104 via RS-232 through converter = send to 1104 OK, can't receive from 1104

Do I understand it correctly that when you send a pre-set ASCII character from HT through the converter to the 1104 that HT receives back an entire intelligible ASCII string from the 1104?

But, that if you send the same character from the KV20LR from its RS-485 port (or RS-2323 port and the converter) to the 1104 that you do not get the same ASCII string sent back to the KV20LR from the 1104?

Dan