Hi,

I try to communicate with a PLC, using the Modbus RTU communication. Much frames are in errors (one out of ten) : the Modbus_RTU_Slave module send the requests (not always regular) but there are only few answers.

After testing different parameters, I used a serial port analyzer to check the requests and the answers.
I found out that Proview sent the request twice, one after the other. So the slave didn't answer.
Sometimes, Proview sent only one request, and the slave answered.

Can you tell me where does the problem come from, please?

Best regards,
Jerome

Salut Jerome,
Pour permettre à Claes de te répondre plus rapidement, pense à poster le maximum d'infos (vues d'écran 'paramètres objets' et vues messages Xterminal).
/Ben

Hi,

As Ben suggested, I give you more informations.
First, I give you my Modbus RTU configuration, in attachment.

I will show you frame captures, with request and answer problems, but I have to set my platform back, so I need time. Maybe next week...

Thanks to take a look to my problem.

Jerome

Hello Jérôme.

Si j'ai bien compris le TSX est maître (client) ? IL semble quelquefois répondre en plus d'une seconde

1-Mets les tâches sur un thread de 0,1s et les scan interval sur 10

2-Essaie d'augmenter receive timeout à 3s par exemple

/Bruno

Hi,

I made the test back, and I made screenshots, this time.
You can see the 2 cases:

• Frame OK : Proview send the request "01 01 00 00 00 0E BD CE" only once, and the slave send the aswer "01 01 02 0 00 B9 FC". as you can see, the slave answer quickly (less than 30ms)
• Frame NOK : Proview send the request twice, so no answer from the slave.

@Bruno : Le TSX est esclave (Modbus RTU). J'ai changé le Thread (0,1ms) et le Scan_interval (10), c'est plus stable mais j'ai des requetes toutes les 1,5s (10x0,1=1s ). Pour le Receive_timeout à 3s, ça met proview en défaut (running en rouge), donc je suis revenu à 500ms. De toute façon, l'automate repond rapidement.

Jerome

Hi Jerome,

It looks as if the screenshots are identical.

/Claes