We are the (hardware) engineers behind the Photon; Ask us Anything!


#1

Brett, Mohit and Will here, the engineers who designed and built the new Particle Photon. Here’s the initial announcement about it and here’s the recently posted Photon changelog. We’re here until 3pm PST today, so Ask Us Anything!


Particle AMA on Wednesday 5/27: Photon Engineers
#2

Where is the AMA… here?


#3

Yep! Go for it!


pinned globally #4

#5

Ok, hardware guru type guys, now that the Photon is in full swing and the Electron is in motion, will you be focusing on shields next?


#6

We have been focusing on the shields in the background all the way. The Photon manufacturing took higher priority and now that they are beginning to fly out the door, we’ll focus on getting all the shield flying.


#7

our product had a reasonable battery life based on the measurements you took of 60uA, but the new specs of 160uA halve the expected life since it is in deep sleep mode mode most of the time. Unfortunately, the battery size is already constrained.

Can you please explain why we’re not seeing much greater efficiencies from the new ADC? (i.e. the old ADC on the core was blamed for the 180uA in deep sleep)

I also wonder if you have any other suggestions to reduce current draw to extend battery life.


#8

What was the best part of developing the Photon?


#9

Ok, @mashandburn is asking a great question so I better shape up. I expect to make relatively small run boards using the P1. Can I treat it as an SMD and reflow solder it in my (controlled) toaster oven?


#10

How did you manage to fit all the same and more components on a single side of the Photon? Were there any tough trade-offs? How many RF switches did you accidentally inhale?


#11

The Core seemed to have a bit to long time delay, when it needed to be re-connected to cloud. How much better at this is the Photon?


#12

@peekay123
The answer is absolutely yes! The P1 modules are much easier to hand place and you can totally expect them to reflow nicely in a temperature controlled toaster oven. Early prototypes at Particle were successfully built both on a skillet and in a small reflow oven!


#13

@peekay123 My next question was going to be about favorite ice cream flavors, but now I’m really curious about the answer to your solder reflow question!


#14

I hand-assembled one Photon with @will and used about 5 RF switches. One ended up on the board. The location of the other 4 are currently unknown.


#15

@mashandburn, I love ice cream! I don’t think the ADC was the issue with the Core power. It was the external flash chip and the LVR that both had no “off” mode causing the higher than expected deep sleep current draw. :smiley:


#16

Those dang RF switches are really small. Fun fact–the pitch on those bad boys is 0.35mm, and most contract manufacturers can handle a minimum of 0.3mm…so hand placing them was definitely a pain in the butt.


#17

You guys should have used trained fleas to do that. That switch is a bit smaller than a flea if I recall :wink:


#18

This actually depends on several factors like the wifi gear used, network congestion, distance from the router etc. Technically, the Photon should connect quicker since its faster than the CC3000 module.


#19

@mashandburn great question! The 60uA number that I posted in github was a preliminary measurement from one photon. I also took measurements from two others at the time… one was 160uA and the other 187uA. I chose to stay conservative and go with 160uA in the datasheet for now. I haven’t had a ton of production photons come my way for measurement, but they are starting to flow from the manufacturing gates now and this number will be updated soon!

The ADC on the Core does not attribute that much quiescent current AFAIK, it was the 120uA of quiescent current from the LDO which remained on all of the time. The SMPS on the Photon has a quiescent current of 50uA and shutdown current of 0.1uA. We also exposed the enable pin on the bottom of the Photon. All of the details of the lowest power modes and methods to get there on the Photon are not fully explored at this time, but it is definitely a high priority with the Photon. We also have access now to the VBAT pin which has a max current consumption of 19uA stated in the STM32F205 datasheet. We will update the community with a nice tutorial of how to implement the lowest power consumption with the Photon out of the box, and with add-ons in the future.


#20

As of last week, the VBAT was not controllable by software. Is that a change in the works?