Hardware Items

Owned by James Hughes
Last updated: Aug 14, 2021
4 min read

Considering the thread solved and closed as of Aug 14, 2021 . LDO replacement solves RESET on power up of WiFi radio and secondary, less frequent RESET issue solved by moving ISR to SRAM for execution.

Hardware Issues/ Enhancements

ISSUE Stronger power supply. 5V operation works, but 3.3V battery does not. Starting to see evidence that this may be an issue with my build. Need to keep open minded.

  • Upgrade from 200mA LDO to 500mA LDO solved my RESET issue.

    • Now using TC1262-3.3V LDO

ENHANCEMENT Hall Effect sensors on measurement devices
ENHANCEMENT I2C based counters for rainfall and wind anemometer revolution count
Enhancement Full low current analysis
Mount ESP32 on PCB and keep only what I need in the design

Troubleshooting the RESET issue I see on my PCB

  1. When RESET or initial power on happens on non 5V USB power (using LiIon battery and MCP1700)

    1. WiFi radio begin() will fail and system reboots

    2. second connect will pass

    3. sequence fails again after deep sleep and timer WAKE

  2. TODO: Scope 3.3V supply and look for any signs of droop

    1. monitor regulator output and 3V3 pin on dev module

  3. Jul 1, 2021 Observed that fully charged battery will RESET controller after deep sleep, but as voltage gets < ~4.1V controller stops resetting.

Jul 1, 2021 4:30am - Experiment start

Jul 1, 2021 19:10pm

  • MQTT topic added to report boot count

  • Boot count starts to increment after deep sleep, but microcontroller randomly still RESETs

  • I now have a way to know when things are working properly

  • One can clearly see when boot count is getting RESET to 0

Left graph: ADC reported battery voltage vs. time

Right graph: bootCount vs. time

**Notice how bootCount periodically resets after incrementing for some time. This is typical behavior is the ESP32 RESETs when activating WiFi radio.

Jul 7, 2021

I replaced the MCP1700 with a TC1262-3.3V LDO (500mA) and the system works on a fully charged battery immediately! I’ll post results from overnight run to see if any system resets occur.

bootCount vs. time with 500mA LDO

Jul 8, 2021

Happy to report that I ran overnight without incident!

Long term TODO:

Hall Effect sensor based wind and rainfall measurement
I2C based wind counter, easier to periodically read instantaneous wind values with ULP
Layout ESP32 on main PCB, get rid of the dev module entirely
Really attack the deep sleep current support
Add FET switch for powering down all peripherals while in deep sleep
No power LED constantly drawing current
LoRaWAN stack

 

Log of efforts

Power supply reboot debug issue

Jun 22, 2021 Ordered 500mA LDO’s from Microchip. TC1262 (qty 10)

Jul 8, 2021 New LDO works great! Very haphazardly tacked on the existing PCB design, but no more brownout and RESET.

 

Battery Life Testing

Using a 3100mA LiIon cell

Jul 8, 2021 6am, battery testing with 15min timer settings to evaluate battery life with no recharge

Jul 11, 2021 4am battery voltage falls < 3.7V

Current Measurement

Mode

Current

Mode

Current

Deep Sleep

~20ma

Wake

???

Wake with WiFi

~120ma

DEV board and deep sleep current capabilities are not compatible with each other

Thomas was able to get sleep current <1mA when removing the power LED and the USB to UART converter chip.

 

New PCB arrived

Aug 4, 2021 Thomas designed a PCB version that accepts the new LDO. I’ve been examining the new board and experimenting with it.

Aug 9, 2021

NVM rainfall backup looking more appealing every day.

Aug 10, 2021

Disappointed that I’m seeing RESETs, but found something in my code

 

//Average samples if (msTotal || samples) { windSpeed = 1.49 * 1000 / (msTotal / samples); }

My logic to check for divide by zero is wrong. Should be &&

 

//Average samples if (msTotal && samples) { windSpeed = 1.49 * 1000 / (msTotal / samples); }

 

Running boot experiment without sensor connected now. msTotal and samples will both be zero and this case will never happen.

After running 1000 boot cycles without incident, I’ve proven to myself that the secondary RESET issue was caused by software.

Aug 11, 2021

Now at 1800 boot count with no issues. Hardware is stable.

 

Aug 14, 2021

Secondary, intermittent reset issue seems to be solved by properly marking ISR routines to be copied to SRAM.

IRAM_ATTR in function definition informs program to copy and execute code from SRAM.

//======================================================= // windTick: ISR to capture wind speed relay closure //======================================================= void IRAM_ATTR windTick(void) { timeSinceLastTick = millis() - lastTick; //software debounce attempt //record up to 10 ticks from anemometer if (timeSinceLastTick > 10 && count < 10) { lastTick = millis(); tickTime[count] = timeSinceLastTick; count++; } }