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rS485 shield for PI


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#1 jim

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Posted 12 October 2014 - 02:11 PM

Dear Tech Support:

 

I am following the instructions on the wiki http://learn.linkspr...shield-for-rpi/ and am able to read data from my PC USB2RS485 device, however, attempts to write data results in dropped bits. The tx/rx lights on both the shield and my PC USB device light when the data is sent from the Pi, however, I'm unable to read the data correctly. I've tried several PC "terminal" type programs including reading the comm port directly via a program that I wrote.

I've tried writing via Python (the linksprite example), Java and minicom on the PI. All have the same result....reading is fine (data sent from the PC), however, data send back to the PC is not complete.

Can you offer any help with this problem? Thank you.


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#2 jim

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Posted 12 October 2014 - 02:13 PM

Hi,

 

Now it's difficult to tell which part is wrong. Can you use something like a TTL UART to USB convert to connect to your UART of Rpi, and to check if the UART is working at intended. if it does, then the RS485 shield is bad. 



#3 WoutD

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Posted 04 March 2015 - 01:15 PM

If anyone has a solution for this, I would be really thankfull. Because I encountered the exact same problem...



#4 NL7559kw

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Posted 09 November 2015 - 04:53 PM

Not the same question, but very related.
My plan is to interface a kWh-meter type DDS238-1: it has a 2-wire RS485-interface applying Modbus-protocol.

;-) One step further than just message-handshaking.
Any forum-member with Modbus-experience applicable for this RS485-interface & Raspberry?






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