RESET sources 45MA on HTCC-AB01?

[groth99]

I built an external watchdog mcu because the builtin one requires waking the part too often. It wasn’t resetting the part.

Connecting a multimeter between the RESET pin on HTCC-AB01 and ground I see 45MA current.

The schematic says the pull-up on RESET is 10k. I presume it is actually the auto-boot circuit is causing the problem.

Is it safe to work around this by adding a mosfet to pull reset down harder or could that cause damage?

Is there a better way to trigger a reset externally? If not, you might consider adding a resistor between G2.D2 and RESET (1k? 470?) in a future revision.

Is there a more detailed schematic or data sheet for G2 on https://resource.heltec.cn/download/CubeCell/HTCC-AB01/HTCC-AB01_SchematicDiagram.pdf ?

[jayjay]

Hello,
If you want to properly use the watch dog on this series checkout my post here:

lowPowerHandler(); & TimerLowPowerHandler()

Hello @peterm OK after digging a bit deeper i found the following solution using the innerWdtEnable(true) instead of innerWdtEnable(false) which will auto feed the WDT when enabled and awake. but in order to make it work and have the WDT disabled while asleep we would need to stop the WDT interrupt when not required since that’s what keeps waking up the board from sleep to feed the wdt. using the following code: int count=0; void setup() { /* Enable the WDT, autofeed */ innerWdtEnable(true…

this should help you set the watch dog correctly without it waking up after few seconds

cheers,
Jay

[groth99]

Having the watchdog disabled while asleep seems like a reliability risk -> the system can sleep forever without getting reset. I also don’t like the auto-feed strategy. I want the watchdog to be reset only when actual system work is completed.

I am much happier with a relatively simple external watchdog that supports appropriately long intervals for sleepy sensor devices. In my case an ATTiny1614. It also provides some sram to stash join state and frame counters assuming I can ever figure out how to save/restore that state. I do wish someone from HelTec would confirm it is safe to pull down the reset line hard for ~2 seconds with a mosfet. This seems like a hardware bug.