Boron / Xenon / Argon Carrier for Outdoor Applications


#82

@shanevanj,

OK, but what if we connected the RTC to the EN pin instead of the D8? That way, the Alarm would turn on the power for the device itself. For now, we can table this but it could be something to look at in the future.

So, proposal is to go with @rickkas7 RTC and library integrated into this board.

Chip

Chip


Better Battery Life for Delightful Particle Mesh Deployments
#83

I use a slightly different circuit with the MCP79410 to control the EN line on the Boron. It also requires a NL17SZ74 flip-flip, some N-channel MOSFETs (2N7002) and pull resistors.

Using this circuit the idle current drops to around 75 uA which gets pretty good battery life. This is only recommended for long sleep durations; I wake once a day.

It does not use an external coin cell or supercap. The VBAT pin on the RTC and VCC on the flip-flop connect directly to the Li+ pin (no regulator required).


#84

I think this is a nice application of this RTC and would work well for longterm or short term sleep with perhaps a jumper (A-com-B type), that allows the wakeup to either go via driver circuitry to EN or to a wakeup pin (perhaps also an IO to detect the watchdog “mode”)


#85

@rickkas7,

Thank you for sharing this circuit. I am planning to use the MCP79410 on the carrier board in large part because of the great library you have provided.

I want to make sure I understand your circuit and I apologize if these are basic questions. Please let me know if I have this right.

  1. This circuit will provide a reliable time source that can enable the Boron to go to DEEP sleep and resync its time when it wakes without having to connect to the Particle cloud.
  2. This circuit is more about putting the Boron to sleep for extended periods (such as overnight) by controlling the Enable pin. If I was looking to have the device sleep for shorter periods, I could connect the multifunction pin to one of the GPIO pins on the Boron and wake using an alarm.
  3. The Flipflop and the FETs are used to control the Enable pin and therefore must be powered by VBat so they - along with the clock - can function when power is off.

Thank you

Chip


#86

@shanevanj,

I agree that they buried the lead here but, on page 21 of the datasheet, it does say that the alarm interrupt function is available on battery power.

So, looks like we have a winner.

Chip


#87

Yes, you are correct. There is no electrical reason you can’t use it to go to sleep for shorter periods. however the EN line powers down the modem and you will use significantly more power reconnecting to cellular than you would use SLEEP_NETWORK_STANDBY for sleep periods less than 15 minutes or so.

Since the 3V3 line is not powered when EN is low, the RTC and associated circuitry must be powered from Li+. Since that can be as high as 4.2V, the MOSFETs prevents high voltages from damaging the GPIO or applying a voltage higher than 3.3V on the EN line which has a pull-up to 3V3.


#88

@rickkas7,

To power cycle your device, you could set an alarm for 10 seconds into the future and then bring D3 high. This would pull the EN line low and then the alarm interrupt would bring EN back high when the alarm goes off. Right?

Thanks,

Chip


#89

All, I have redesigned the board to incorporate @rickkas7 's Real Time Clock circuitry and all the other great suggestions from this group. My plan is to get a small batch of these made at MacroFab (if I am brave / confident) or have one more run of boards from OSHPark if I am not.

Changes - New Features:

  • Physical switch to turn off everything on the board but the RTC battery backup for storage and transport
  • Turning on the switch enables the RTC which can manipulate the EN line to reduce power consumption and then wake the device at a preset time.
  • The Alarm functionality will also allow the device to “hard reset” or power cycle itself

Please look at the schematics and let me know if I have made any major mistakes.

I am not sure how to offer the RTC functionality if there is no LiPO battery. To be honest, I am not sure how important the RTC is if you are operating the Boron without a battery. Comments welcome here.

Once I am sure about the schematics, I will redo the layout.

Thanks,

Chip