Comm using a LED and 2 spare I/O pins
John Bond
Posts: 369
Here’s a bit of fun, a little bit of make-believe…
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You have an order for a device. So you’ve finalised the design, produced the PCB and are about to stuff components and assemble the devices. The customer suddenly realizes he needs to regularly update the program in the field. You’ve not allowed for any communication. All you’ve got is a LED on the outside of the box that you flash using one pin of the Micro and you have a second unused pin. Oh what to do! What to do!
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Have a look at this paper on using two pins and a LED for comms. (of course if they’d used an SX, they’d have been able to rewire the crystal port.)
By the way, I've often read about how good two matched LEDs work for slow sensing. I played with this circuit over the weekend.·You pulse the one·LED·and reverse bias the other to·an·input·pin.
Regards from Africa
John Bond
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·
You have an order for a device. So you’ve finalised the design, produced the PCB and are about to stuff components and assemble the devices. The customer suddenly realizes he needs to regularly update the program in the field. You’ve not allowed for any communication. All you’ve got is a LED on the outside of the box that you flash using one pin of the Micro and you have a second unused pin. Oh what to do! What to do!
·
Have a look at this paper on using two pins and a LED for comms. (of course if they’d used an SX, they’d have been able to rewire the crystal port.)
By the way, I've often read about how good two matched LEDs work for slow sensing. I played with this circuit over the weekend.·You pulse the one·LED·and reverse bias the other to·an·input·pin.
Regards from Africa
John Bond
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
