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necroware / nwX287

Drop-In replacement for Dallas, Benchmarq, Odin and other RTC modules
GNU General Public License v3.0
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Modifying board to include jumpers to change pin 1 function #13

Closed tomstorey closed 8 months ago

tomstorey commented 1 year ago

Following a recent video on Adrians Digital Basement where this module was used in a machine that required Motorola bus mode to function, and seeing the modification made with a bodge wire, I thought it would be good to include some solder bridges that could be used to implement a cleaner solution to make this module more universal.

Two 3-way solder jumpers have been included that allow pin 1 of the RTC chip to be routed either directly to pin 1 of the socket/header, or to a second 3-way solder jumper which allows selecting between a hard pull up or down. Hard pull up/down is used by recommendation of the datasheet for the MC146818A and bq3285.

The project format has been updated to KiCad 6 as a result, since that is what I use. Sorry! :)

necroware commented 1 year ago

Hi! Yeah, I already prepared the same change, but I used only one "jumper", where VOUT is connected to the middle pad and goes to the BQ3285 and two other pads are either VCC and GND. If you don't solder the bridge, VOUT is directly connected to the IC as is and if the mainboard doesn't pull up/down the VOUT you have to bridge one of the pads to the middle one.

The question now, why do you think you would need two jumpers for this?

tomstorey commented 1 year ago

Why 2 jumpers?

As long as only one side of each solder jumper is ever bridged at a time there are less ways that you can potentially damage something, or feed a logic level back out to the mainboard and interfere with something that is going on back there (without needing to cut the pin off the header for example).

I guess its was just ultimate flexibility. :)

necroware commented 1 year ago

Hehe :) Sounds slightly over engineered and you still can get it wrong if you want to. The only one thing, which would really help against back pushing is a diode, but also that would be too much IMHO. One jumper is enough I guess, which would behave in default as it is now and if your Board, where you use it has a floating pin 1, then, you can bridge the required pads.

As I said, I already have made the rev 2 with this modification and some slight cleanups. I'll update the documentation and make a release in the next days. Still, thank you very much for your input! I was not sure, if It's worth it to release this change and It's nice to know, that you think it is.

necroware commented 8 months ago

Completely forgot this one. I finally uploaded my solution. This one is impressive, but I think, there is no need to overengineer it, so let's go with one simple jumper.