Sensor

This topic describes the common questions about smart sensors to help you troubleshoot problems.

How does the low power mode work?

• For the MCU SDK solution, the module is powered off when entering an idle state. The MCU can control the on/off state of the module. It communicates with the module through a serial protocol.

• For the SoC solution, sensors run in deep sleep mode when entering an idle state. You can wake it up from deep sleep by either AON timer interrupt or GPIO interrupt.

  If you want to connect your MCU with Tuya’s network module through the MCU SDK, submit a service ticket.

How long does it take for a low-power sensor can report data after waking up?

• For the MCU SDK solution, after the module wakes up, the MCU sends data to the module on receiving the current network status. Then, the module reports the received data to the cloud. If the network works fine, it will take about three seconds to complete this process.
• For the SoC solution, after the module wakes up, it will perform initialization and connect to the router. After connecting to the cloud, it can report data.
  • The Total Time = Initialization + Cloud Connection + Data Reporting
  • If the network works fine, it will take about three seconds to complete this process.

Why the log shows the sensor is restarted after waking up?

• For the MCU SDK solution, after the module wakes up and is connected to the cloud, it will report the status as a restart. Actually, it means power-on, and the parameter is 0.
• For the SoC solution, the so-called restart also means power-on and the parameter is 0.

Why is there a peak pulse every two seconds when the sensor sleeps?

For the SoC solution, the internal low-frequency oscillator acts as the clock when the sensor sleeps. It performs calibration every two seconds. The maximum calibration frequency is two seconds. You can adjust it through the register.

What is the time drift for a wake-up timer?

Our test result indicates that a 10-hour wake-up timer can have a time drift of 25 seconds.

How does the OTA update work?

• For the MCU SDK solution, the MCU sends a command to accept an update, then powers the module off and waits for a confirmation from the mobile app. The module performs the update on receiving the confirmation. After the update is installed, the MCU powers the module off.

• For the SoC solution, a manual operation can make the sensor’s LED indicator steady on, meaning the module is waiting 60 seconds for an update confirmation from the mobile app. The LED indicator will be off after the module receives the confirmation and starts downloading the update. If the download times out after 120 seconds, the module enters sleep mode.

  The manual operation indicates that after the sensor wakes up, the user needs to press a specific button five times within three seconds.

How long do two dry batteries last in an SoC sensor?

For SoC sensors, the contributing factors to calculating the theoretical daily battery usage include the total time from waking up to reporting data until entering sleep mode, the average current in this process, the times of daily wake-up, and restarts due to wake-up timer. Assume that the total time from waking up to reporting data until entering sleep mode is 12 seconds, the average current in this process is 73 mA, and the times of daily wake-up is 10. Then, the theoretical daily battery usage ((12 × 73) mAs) × 10 × 2 ÷ 3,600 = 4.87 mAh. Assume 80% of the capacity of the two dry batteries is available. We get the theoretical battery life: 1,500 × 2 × 0.8 ÷ 4.87 = 492 h.

How does an SoC sensor work and indicate status in poor network conditions?

If the network performance is poor, the sensor will enable a 40-second timer to verify if its connection with the router is active. If getting no response within 40 seconds, the sensor enters sleep mode and its LED indicator will be steady on for 10 seconds to indicate an offline status.

What is the supply voltage for the module in a battery-powered sensor?

You can use a buck-boost converter to provide a stable 3.3V supply.