And a little preview. 
nRF9160 Feather - Suggestions for next version
Hi Jared,
as for now, in my opinion, 3.3V helps the āmakersā. Quite a lot of sensor boards are for 3.3V (or 5v). To craft the first 100 devices will benefit from 3.3V in my opinion. I consider, that in the most cases, itās decided with that 100 to either build a product or not. So for me, 3.3V is preferred.
The other idea would be to connect the ābatteryā direct to the modem and make VDDIO āconfigurableā. That depends on the other ICs on the board, if that works. And for me, itās not that important.
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Just for those, who are interested; thatās a nRF9160 feather v5, running from a 2000mAh LiPo for about a year. Exchanging a message with encryption over CoAP/DTLS 1-2 CID.
@AchimKraus thank you for sharing!! The chart is also fantastic.
Iām still a bit of a noob compared to Achim and zpm, but my view is that you should keep it to 3.3v - Even if there would be powersavings by going to 1.8v, it it already so low that pushing it even more wont really matter, but as you also state, the hurdles to newcomers might be significant since a lot of other stuff out there needs 3.3v.
We use GPS on some of our things, but I did find it a bit odd that it was included by default rather than being an āaddonā initially.
RGB LED is no doubt a great addition, and iām looking forward to eSim!
Thank you @JeppeMariagerLam for your feedback 
JeppeMariagerLam We use GPS on some of our things, but I did find it a bit odd that it was included by default rather than being an āaddonā initially.
Can you elaborate more here? Iām not sure what you mean. The fact that you needed a separate antenna?
jaredwolff yes, we have an external antenna, for example mounted on the top of a car rather than inside the steel box where the unit is connected to power.
jaredwolff
Hi Jared,
Like the majority of the āmakersā, nearly all the sensors I use are 3.3V. However, for the longer term, I think itās worth having a configurable 1.8-3.3V VDDIO if not much additional effort.
Are you planning on driving the RP2040 at 3.3V or in addition also thinking of using 1.8V, as RP2040 does support multiple power options?
Will there be an option to shutdown RP2040 if nRF9161 is in a sleep mode?
Any plans to bring out any of the GPIOs from the RP2040 to the Feather pins?
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@zpm1066 thank you for the amazing feedback! 
zpm1066 Like the majority of the āmakersā, nearly all the sensors I use are 3.3V. However, for the longer term, I think itās worth having a configurable 1.8-3.3V VDDIO if not much additional effort.
It is possible actually with the nPM1300. The only part that wouldnāt work is the onboard NOR flash. It does not support such a wide voltage range. They have 1.8V variants and 3.3V variants. My thoughts would be to go with the 3.3V version and if any flash writes need to occur the buck needs to be placed into 3.3V mode. Testing is still necessary since Iām not sure how the flash would handle 1.8V. If it ends up leaking tons of current that would put the kibosh on it right there.
zpm1066 Are you planning on driving the RP2040 at 3.3V or in addition also thinking of using 1.8V, as RP2040 does support multiple power options?
Right now, thanks to all the feedback thus far, the plan is to run it at 3.3V. It does have a separate VDDIO pin which allows for running the IO at 1.8V. It does require 3.3V for USB (which is critical for this board!) on the other power supply pins no matter what.
zpm1066 Will there be an option to shutdown RP2040 if nRF9161 is in a sleep mode?
Good questions. Itās the reason why Iām asking you guys your preferences on IO voltages. 
By default itās on on a cold boot but then is configurable in software to be shutdown when not in use. Both buck converters actually can be configured in āretention modeā which lowers the rail voltages when in a sleep mode (very neat).
zpm1066 Any plans to bring out any of the GPIOs from the RP2040 to the Feather pins?
No plans since itās mostly meant to be a programming IC. All the GPIOs are going directly to the nRF9161.
jaredwolff By default itās on on a cold boot but then is configurable in software to be shutdown when not in use. Both buck converters actually can be configured in āretention modeā which lowers the rail voltages when in a sleep mode (very neat).
Wonderful! Your nRF9161 Feather is looking fantastic!
Btw - Any decision on which RP2040 debug probe firmware (probe-rs or raspberrypi debugprobe) youāre leaning towards? probe-rs development seems to be pretty active. I havenāt yet tried either but plan to in the next month or so.
zpm1066 no choice yet. The CMSIS-DAP C implementation is slightly faster. I havenāt gotten there yet though. Stay tuned
I guess, itās a too specific use-case, but I would welcome, if the board offers a 8-pin EEPROM solder mask. I would equip that with an HSM (ATECC608A) and use that for the encryption with tinydtls.
I know, that the nRF9161 offers TF-M as well and so a HSM may be considered to be obsolete, but for portability itās easier to keep the keys in such a device as the ATECC608A.
@jaredwolff
Perhaps a little late but is there any chance of adding an I2C/STEMMA connector for sensors, OLED, EEPROM, etc? Not sure if there is any space on the reverse side of the board. It would be pretty useful for expansion. Thanks.
Thanks for the suggestions. Iāll definitely keep them in mind.
16 days later
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AchimKraus Thingy:91 is missing expandability and a DK is just to large in size.
Recently Nordic Semi has been making a few changes to the Thingy91:X devicetree files, e.g. added support for the expansion board and other misc changes. I donāt see an āedge_conenctorā defined in the "āthingy91x_nrf9151ā devicetree yet like in nRF5340. Somewhat slow progress at the moment, perhaps there are delays in nRF9151 availability.
I expect the Thingy91:X Expansion Board will be the same spec as that in the Thingy:53 (nRF5340) or an enhanced version with backward compatibility. The nRF7002-EB WiFi 6 ( I use several with Thingy:53 and nRF52840 boards) should work with the Thingy:91X. With I2C (EB and I2C STEMMA), SPI and several GPIOs, the Thingy:91X should be pretty expandable for sensors and peripherals.
Originally, both the Thingy91:X and nRF9131-EK were planned for Q1 release. Hopefully weāll see a Q3 release.
Yea it will be cool to see. Who knows I may base a new board off of the 9151 First thing is first, gotta finish the 9161 version!
a month later
Proto 2 has been on my desk for a few days now. Iām trying to figure out whatās drawing so much current with the programmer disabled. (Getting 1mA in active sleep whereas it should be < 10uA)
I think itās going to have to come to removing parts until I get the expected current. 
Weāll see!
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jaredwolff Looks great! Whatās the beige connector? I2C STEMMA?
zpm1066 jaredwolff Looks great! Whatās the beige connector? I2C STEMMA?
Currently connected to the SWD lines for the RP2040 for programming with an external Picoprobe
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Now weāre talking!
Average of 6uA in sleep mode at 3.6V. That includes the LIS2DH and the external flash in sleep/power down. Slightly better than the current nRF9160 Feather at ~10uA.