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st3485EC rs485 to uart problem

Question asked by Raider E on Mar 12, 2017
Latest reply on Aug 28, 2017 by sachin singh

Hi Everyone,

 

I ma using the st3485EC rs485 to uart interface to send/receive data to 485 device. I transmit data with no problems and i can see the device replying back with some strings. However, I am not able to receive anything on the uart rx pin which is pin number one on the chip above. Now I suspect that my connections might be wrong. I am connecting the RE(active low) and DE (active high)togather  to one of the GPIOs, assuming that when i transmit i set that gpio pin to high and when receive set it to low. Even read it somewhere else that this is the most common way of doing it. However, this contradicts the datasheet and i suspect that could be the cause. The data sheet truth table says if DE is low and RE is high the chip goes into shutdown mode. I scoped pin 1 on the chip and its dead nothing i get but on transmitting pin 4 its all good. Anyone has experience with this chip and would be great if you can post the sequence of tuning the enable pins on and off to enable the  receive and send

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