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The diagram does not show the RTS connection to the connector JP9.
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The U2 chip does not have pin numbers 1…8 and does not have the brand name SP3485.
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The VCC voltage change limits are not specified, for example 3.3V or 3.3-5V.
1 - Good point, it’s not shown in the schematic but it’s pin 4 on JP9
2 - If you cross reference the data sheet, pin numbers show up there, & looks like the schematic shows sparkfun’s internal part number.
3 - From the “features” section on the product page:
- Operates from a single +3.3V supply Interoperable with +5.0V logic
It looks like this is a pretty early product from sparkfun from before they refined their schematics.
Thanks for the answer. And how would you comment on the non-standard resistor R4 220 Ohm? According to the RS-485 standard, it should be 120 Ohm to match the wave resistance of the cable.
Sorry, don’t know why they chose that value but i have used these breakouts on 100’s of feet of random wire I had laying around and they worked fine.
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