SHT31 Review + Preliminary Understanding of Evaluation Board

hujj

SHT31 Review + Preliminary Understanding of Evaluation Board [Copy link]

 

After receiving the evaluation board, the first thing I did was to read the user manual. My English foundation is poor, so I can only learn with the help of Baidu Translate. The following is the user manual annotated by Baidu Translate:

SHT31_SmartGadget_UserGuide.pdf (896.01 KB, downloads: 6)

2019-12-24 12:28 上传

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By reading the user manual, I know that the button on the evaluation board can switch the display between humidity or dew point temperature when it is short pressed. The first line of the figure below shows the humidity value:

After pressing the button, the first line shows the dew point humidity:

Long press to turn Bluetooth on or off. The following picture shows Bluetooth turned on and the Bluetooth logo appears on the screen:

When you start turning on Bluetooth, the last four digits of the Bluetooth address will be displayed on the screen, as shown below. My evaluation board shows 3d5b.

This address is also displayed when searching for Bluetooth devices on the phone:

This may be due to the inconsistency of the Bluetooth version. The mobile phone cannot receive the data sent by the evaluation board:

It keeps saying "Connecting to Smart Humigadget [rssi: -51]...."

Since the official mobile app has not been available for download, further testing is not possible.

This content is originally created by EEWORLD forum user hujj . If you want to reprint or use it for commercial purposes, you must obtain the author's consent and indicate the source

hujj

There are three DEF files in the hardware data I downloaded:

2214018_V4_SmartGadget_BOM.pdf (17 KB, downloads: 4)

2019-12-24 13:16 上传

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2214018_V4_Schematic.pdf (97.71 KB, downloads: 6)

2019-12-24 13:16 上传

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2214018_V4_Assembly.pdf (983.16 KB, downloads: 5)

2019-12-24 13:16 上传

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The first file above is the component layout diagram of the PCB board. From the diagram we can roughly understand the location of the main components of the evaluation board.

The second file above is the circuit diagram:

It can be seen that the evaluation board is mainly divided into three parts. The first is the sensor in the upper left corner, which is the hollow part of the board. It transmits data through the I2C bus. There is also a four-wire interface position on the back of the PCB board to facilitate everyone to test the sensor:

The display part is a segment code LCD, which is controlled by an NXP MC9S08LL8CGT eight-bit microcontroller. This 48p chip is soldered between the LCD and the PCB board, and communicates with the main control part via SPI.

The main control part is a 26p chip, marked with the model "BVMCN5103". I can't find any relevant information on Baidu and other websites. I believe this is a single-chip microcomputer chip, which is responsible for obtaining data from the sensor, processing it and sending it to the display part. The corresponding debugging point of this chip is ST1 on the back of the PCB board, which provides 3V power supply, ground wire, TX and RX for serial communication, and SWDCLK and SWDIO interfaces for downloading and burning.

The ST2 debugging point on the back of the PCB board corresponds to the eight-bit microcontroller of the display control. In addition to the 3V power supply and ground line, this debugging point only provides two signal lines, RESET and BKGD. It is unknown what signal this BKGD is.

I originally planned to further develop the potential of this evaluation board by downloading and burning the code, but I don't know the information of the main control part of the single-chip microcomputer, so I can't experiment for the time being. What I can do now is to find a way to use the expansion board to lead out the relevant interfaces of the evaluation board first, so as to prepare for the next test. In addition, I am considering adding a shell, a lithium battery and a charging control module to increase some practical functions.

dcexpert

nRF51822 supports micropython. If you have a chance, you can try to use micropython to read the SHT31 sensor.

hujj

dcexpert posted on 2019-12-24 14:35 nRF51822 supports micropython. If you have a chance, you can try to use micropython to read SHT31 sensors.

You should also be able to try to read the data of SHT31 from the sensor I2C interface on the back of the PCB board, but doing so only utilizes this sensor, and other control and display parts are not utilized.

caizhiwei

By the way, the main control should be nrf51822, no need to search for "BVMCN5103".

Haha, thanks for sharing!

hujj

caizhiwei published on 2019-12-24 17:28 By the way, the master control should be nrf51822, no need to search for "BVMCN5103", haha, thanks for sharing!

Thank you for your advice! Otherwise I will still be stuck in this pit.