Electronics > Projects, Designs, and Technical Stuff

Multiple UART on AVR controller

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slowe:
UPDATE FIRST POST WITH NEW SCHEMATIC

razvan784:
The SMAJ series TVSs have quite high capacitance, which is not a problem for serial lines but may cause USB communication to be unreliable or fail completely. There are low capacitance TVSs or ESD diodes that are specially designed for USB applications or for high-speed digital lines.

On the DE/RE line you may want a pull-down resistor instead of a pull-up, so it defaults to disabling the 485 driver.

slowe:

--- Quote from: razvan784 on July 30, 2021, 07:56:35 pm ---The SMAJ series TVSs have quite high capacitance, which is not a problem for serial lines but may cause USB communication to be unreliable or fail completely. There are low capacitance TVSs or ESD diodes that are specially designed for USB applications or for high-speed digital lines.

On the DE/RE line you may want a pull-down resistor instead of a pull-up, so it defaults to disabling the 485 driver.

--- End quote ---

Ok I found the TPD2EUSB30A, but it is not available on Farnell, I don't find same chip....

Ok for DE/RE

slowe:
And there you have it, I finished the card with a lot of advice I received!

So I worked hard on the diagram for:
- Have a correct power supply,
- Protect RS485 / RS232 and USB
- Combine the 3 interfaces on a single UART

Thanks everyone!

Bassman59:

--- Quote from: voltsandjolts on July 30, 2021, 12:51:54 pm ---Hmm, Maxim. Yuk.
Always nice to have a plan B, especially with Maxim.

--- End quote ---

While everyone agrees that Maxim the company sucks balls, their various RS232 transceiver/level-shifter chips are widely second-sourced. I've used the MAX3232 from TI in a few designs.

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