TTL UART to RS485 Converter Module (CE05154)

Hi Bob,

I had an inkling I’d need correction from our resident RS485 guru on that post! I’ll remove that from my post.

-James

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Hi James.Guru ???. If you think about it the same thing applies to quality audio circuits. The same pros and cons (more pros than cons) apply. Not rocket science but, dare I say it, Analog techniques
Cheers Bob

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This is literally just TTL to RS-485 - it cannot do RS-485 to TTL without modification.

Again, a real shame the board is so limited in its functionality.

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Hi Ewan
This device IS both ways. Block diagram of the driver…

BUT not both ways at the same time, ie; Half Duplex only.
Please read the above thread completely. You will probably find most of your questions answered.
If you look at the circuit I think R5 and R6 should be removed and R7 only used AT THE CABLE ENDS. That means if you only have 1 device at each end it would be OK to leave ir but if you are using several (read more than 1) intermediate devices this resistor should be removed on those.
What the other pull ups are for I don’t know. All of these resistors are discussed above.

In short if you have one of these at each end of a twisted pair (A & B lines) you should be able to insert TTL at one end and extract the same TTL at the other end BOTH WAYS.
Cheers Bob

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Hi Bob,

For the MAX485 to receive RS-485, ‘RE bar’ (with a line across the top - Receiver Output Enable) needs to be asserted LOW, which cannot be done the way the board is constructed (RE bar, and DE - Driver Output Enable) are both tied HIGH.

My original comment was that this board is simply 'TTL to RS-485 unless modified '.

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And disregard - there IS an output for RE to be set low… Doh!

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Hi Ewan,

Just wanted to say thank you for posting an update to this one after you solved your problem! Now someone else having the same problem can skip all that troubleshooting :slight_smile:

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