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Incorrect switch positions docs in MKR485 Shield's "Getting Started" #9411

Closed fldemarco closed 3 years ago

fldemarco commented 4 years ago

For the Arduino RS485 Shield, on the Getting Started page the 3 DIP switch position functions seem backwards after studying the schematics provided. Can someone verify this is true? Thanks.

graydonhope commented 4 years ago

Can you please link the page you are referring to?

position functions seem backwards?

Can you elaborate on this? What do you mean backwards?

Getting Started with the MKR 485 Shield is this the page you are referring to?

fldemarco commented 4 years ago

Yes sir, that's the document. Back in Nov. I thought the positions of the DIP switches were inverted - the function listed as the OFF position should have been listed under the ON position and vice versa. This was based on trying to follow this schematic: https://content.arduino.cc/assets/MKR485ShieldV3.0_sch.pdf

But maybe it's my ability to read the schematic. And I had to abandon the study of this board. I do plan to pick it up again sometime in the future.

Thanks. Frank

graydonhope commented 4 years ago

@fldemarco I have looked into this issue and see what you are saying. On the MKR 485 shield schematics you will notice they used the MAX3157 microcircuit. I found the MAXIM MX3157 datasheet which includes the pin descriptions and many other useful operating characteristics / schematics that you may wish to use in the future.

Referencing page 11 from the MX3157 schematic, it does appear that switch 2 is reversed. When switch 2 is ON, it makes a connection to pin 14 IGND which is ISOCOM on the MX3157 circuit. According to their description, pin number 10 is the Half-Duplex, Full-Duplex selector and when connected to ISOCOM, it is in Full-Duplex mode.

This is their description for pin 10:

Half/Full-Duplex Selector Pin. Leave open, or connect to ISOCOM to select Full Duplex, orconnect to ISOVCC to select Half Duplex.

I will continue to look into the circuit and read the MX3157 datasheet more so I can provide you with a more detailed explanation and ensure we have not missed anything. If you haven't already done so, I suggest looking at the MX3157 datasheet as well.

fldemarco commented 4 years ago

OK sir. I will. Thanks. Frank

On Mon, Mar 23, 2020 at 2:14 PM Graydon Hope notifications@github.com wrote:

@fldemarco https://github.com/fldemarco I have looked into this issue and see what you are saying. On the MKR 485 shield schematics https://content.arduino.cc/assets/MKR485ShieldV3.0_sch.pdf you will notice they used the MAX3157 microcircuit. I found the MAXIM MX3157 datasheet https://datasheets.maximintegrated.com/en/ds/MAX3157.pdf which includes the pin descriptions and many other useful operating characteristics / schematics that you may wish to use in the future.

Referencing page 11 from the MX3157 schematic, it does appear that switch 2 is reversed. When switch 2 is ON, it makes a connection to pin 14 IGND which is ISOCOM on the MX3157 circuit. According to their description, pin number 10 is the Half-Duplex, Full-Duplex selector and when connected to ISOCOM, it is in Full-Duplex mode.

This is their description for pin 10:

Half/Full-Duplex Selector Pin. Leave open, or connect to ISOCOM to select Full Duplex, orconnect to ISOVCC to select Half Duplex.

I will continue to look into the circuit and read the MX3157 datasheet more so I can provide you with a more detailed explanation and ensure we have not missed anything. If you haven't already done so, I suggest looking at the MX3157 datasheet https://datasheets.maximintegrated.com/en/ds/MAX3157.pdf as well.

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