📡 HS402 WiFi Android Oscilloscope (ESP32 + STM32)

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In the previous article we built 2-channel android-oscilloscope. It was connected to smartphone with USB Type-C to USB Type-C cable. But this oscilloscope can transmit data without wire communication, but it need to attach ESP32 microcontroller module, so in this essay we will do this and make this oscilloscope wireless!

Circuit

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🧾 SCH_HS402-WIFI_V3.0_210327.pdf
🧾 SCH_HS402-WIFI_V3.1_220108.pdf

Power Supply

The ESP need current about 100mA-200mA, peaks could be even bigger, so you can use AMS1117 (Vin = 5V minimum) or TPS73733 (Vin = 3.7V minimum) in 3.0 version or RT9193-3.3 in v3.1 (Vin = 3.7V minimum).

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Battery Monitoring

In the different schematic versions (3.0 and 3.1) the voltage dividers it's also different, note it.

Components list

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🧾 HS402_Component_List_V3.1.pdf

*Tantalum capacitors could be demounted from old PC boards
*RGB-LED should be with common ANODE

Components

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ESPRESSIF ESP32-WROOM-32D module can be bought separately or demounting from devboard, to do that heat the board from below with using hot-air gun:

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Board

The remaining peace of board is for ESP32 module:

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The original idea is to use short connector for STM32-module and standard connectors for ESP32 module, but I've decided to use regular PBS-connectors for both modules.

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💾 PCB_HS402-WIFI_V3.1_220108.zip

Another board

There is also possible to use 30-pin NodeMCU ESP32 module and special pcb-adaptor, made by Denis from the GADGETS playlist YouTube-channel.

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It can be DIY or factory-made (file below):

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🧾 More information:  WiFi_Adapter_Layout.pdf
💾 Gerber files (backup copy): Gerber_WiFi_Adapter_Layout_2021-02-19_11-55-13.zip
📹 Video: https://www.youtube.com/watch?v=TUyCfcAxmac
➡️ Source: https://drive.google.com/drive/folders/1WdWcisx70J...

Mounting

So, find all components and let's started:

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The most difficult part is positioning module, because it has small pin's step.

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Flashing

Download and install Flash Download Tool 3.9.2 from official site (also you can get it reserve copy in telegram-channel).

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Firmware consist of three files, you can get it on GitHub:

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  • ESP32_firmware_V1.4_210408.bin
  • bootloader.bin
  • partition-table.bin

Also you need USB-TTL converter, I have got CH340 based converter, for this chip drivers must be installed manually (download: ch340_driver_win10.zip):

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Open Device Manager (Win + R -> devmgmt.msc -> Enter) and check, that is successfully identified:

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Wire board to converter according to the wire diagram:

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Now connect it to the PC:

Before powering (connection to the PC) press FLASH button and then connect wired module with converter to the USB-port!

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In the software choose sequentially three files ( bootloader.bin partition-table.bin ESP32_firmware_V1.4_210408.binconsistency is important!) and type addresses (0x1000, 0x8000, 0x10000), set SPI frequency 80 MHz, mark Do Not Change and press START:

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Basic information of the chip will be displayed and flashing process will take about 40 s, then just unplug board.

Settings

Connect power supply and connect to HS402-XXXXXX access point (Password: 123456789):

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Open in web-brower IP (after successful connection): 192.168.4.1

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You can set Wifi-name (SSID), password, IP and channel (not required to change):

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That's all, not go test it! Connect phone to  HS402-XXXXXX access point (Password the same, if not changed in settings: 123456789):

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In HScope settings turn on connection WiFi:

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Now it works wirelessly!

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Response rate

Of course, the response between signal connection and displaying is not momentary.

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Tests

CD4050 Hex Buffer as Level-shifter (don't use for loads with current more than 1mA-2mA maximum) for translate 3.3V to 5V:

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Changing PWM-signal 50 Hz pulse width for control servo rotation angle:

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Voltage on inductor in XL4015 buck-converter:

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Catch UART data packet (app has digital module, buy this module not free):

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Video

That's all

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