Endochron Implant

Update time:

I had another look at the ATtiny sleep mode and they seem to have a power-down mode (can be woken with an interrupt or reset) that only uses 0.1uA which is within budget I think (check this mess I guess)

I also ordered a piezo to test if we could do alarms or timers using the RTC to provide interrupts, just a concept really (if that doesn’t work maybe we could have exposed contacts and zap you?). I was also thinking of more than 1 magnet sensor so we can have multiple functions (date, time, timer, something fun).

What does everyone think of having a second microcontroller (like a bootloader) so we can reprogram the main MC over NFC?

A 16 segment display wouldn’t use any more power than a 7 in normal operation so I think we should go with that
image

EDIT: Also this? RGB 7-Segment Digit - 1 Tall Digit : ID 1399 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits

I’m not nearly qualified for my opinion to matter lol

But options are always nice in regards to the 16 segment and boot loader

I do know bootloaders can increase system requirements, and would this cause an increase in hardware requirements? (Likely adding bulk?)

Will the 16 segment actually be able to be taken advantage of? Or would it cause a need for more hardware like above?

A 16 segment will require either a hardware driver (more chips, higher power consumption) or a lot more I/O lines. (Possibly more than are available on an ATTiny85)

Obviously it is capable of displaying more complex sigils, but if the idea is just for an implantable clock then it really isn’t necessary.

Edited to add: personally I was looking for relatively large but low profile LEDs as that would make implantation easier

I’m looking at the 88 as a potential candidate even without the 16seg and it would have enough, and I took apart a 7seg yesterday and it has 2 LEDs per segment, I assume in a 16seg there would be 2 for the large and 1 for the small segments so no more power required

I was thinking of having another ATtiny (smallest one available) that is activated with the NFC chip and acts as a bridge and programmer for the main chip, does anyone know if we could have a single chip program itself? It’s probably possible but self modifying code seems easy to brick

Another thing is would we need a DC-DC step up? and does anyone have a low power suggestion?

one more thing, does anyone think it’s worth putting in a solar panel? (Solar-powered Amal - #13 by amal)

Be careful of the Z-height of these components your considering. We’re probably going to need to arrange for PMMA encapsulation at this point.

Since we’re leaving the uW targets in the dust, it might be worth considering a more capable 32-bit microcontroller that supports in-application-programming over I2C, like the STM32

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Looks like there are STM32 variants that have built in RTCs. Some of the sleep modes support running the RTC simultaneously. Then you just wake the device t with an interrupt from sensors, (like a hall effect or vibration sensor).

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That sounds perfect, have you got a data sheet I can reference?

cd00237391.pdf (2.8 MB)

Looks like we would want the chip in Standby Mode as outlined on page 31. The RTC and external interrupts could wake the MCU.

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Page 84, Standby mode with RTC on uses about 2.7uA which we can manage, and if we can put it into vbat mode we could get down to 0.73uA but this would require another chip that probably uses 2uA or more. This looks good I’ll get one for testing, any preference for which?

We should use eval boards. I’ll take a look for one tomorrow

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I got you, the L1 series is low power, has an RTC, and supports IAP.
I picked this board with an STM32L152RET6

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I have one of these lying around

As you do, that should be enough to test with, I think it has an RTC, and you can test IAP too

Do you have an I2C test card?

yup, I made them. Although I’ll probably do my testing with a NTAG 5 cause it’s better in almost every way

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Can you explain the difference quickly?

Does anyone have Android and/or IOS experience? We need an app to sync the time, configure things (maybe even dynamic configuration, ie the implant sends a template for what can be adjusted), and upload firmware over NFC
I’m happy to try my luck if not

NTAG 5 can output more current for the energy harvesting, it has much better range because it’s ISO 15693 instead of the standard ISO 14443a, it’s I2C communication has many more options, and it’s a much more capable chip that can support cryptography if we want to add it.

I was hoping we could find a workaround instead of using an app. Apps have to stay compliant to the Play store to stay public, and they have to stay up to date for newer versions of Android. What would have a longer lifespan would be a series of raw commands we can send from any device, independent of an app, and a program that can run on the computer using any PC/SC compliant USB reader (like an ACR-122U) to handle if you ever need to do in-application programming. That will be more future proof, so anyone with the correct documentation can make it work, without us needing to build and maintain an app.

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I know its just an example but

Dosnt support anything other than iso14443A & B

I love the idea of having a bunch of commands that are usable from any device!

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I think only supporting programming from a computer is a reasonable thing

Do you mean something like NFC tools advanced commands? Could we possibly allow writing to it as if it’s an NDEF tag?

So people can do this

Instead of this


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Yup. You can enter series of commands to reset the RTC. They’re comma delimited

But what I mean is how will we send them? Raw NFC, or NDEF records? Now that I think about it if the writer check that it wrote properly that might make things difficult