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Vorläufig / Preliminary, work in progress
From company STMicroelectronics there is a powerful low cost ARM®-based 32-bit MCU with 64 or 128 KB Flash, USB, CAN, 7 timers, 2 ADCs, 9 com. interfaces, named STM32F103x8 (64 KByte Flash ROM) and STM32F103xB (128 KByte Flash ROM).
It is interesting that some (most?) STM32F103x8 also have a 128 KByte Flash ROM, explained later.
There are 2 popular boards (3 - 5 EUR) on the market (Ebay, banggood.com, etc.):
STM32F103C8T6 Small System Board Microcontroller, nick name Blue Pill.
STM32F103RCBT6 ARM Cortesx-M3 Leaf Maple Mini Module.
Unfortunately boards delivered from China have usually very little documentation for the usage.
I like to explain the usage with the Arduino IDE (version 1.8.5).
- Low cost (about 24 EUR, if more than one is build)
- Small size (3D printed housing)
Battery powered (LiPo 18650 cell)
- Integrated charge circuit
- Development under Arduino IDE
If you allow a push signal in a MQTT App on a Smartphone, it empties quickly your battery.
- If you want to have a small housing, you need a 3D printer
- You need a lot of background knowledge about software
A mouse click on a picture will expand the picture for better viewing.
A mouse click on a source program will show the listing in a new window with colour coding.
ESP32 Breakout Board
- CPU clock: Standard 80 MHz
- RAM: 520 KB RAM
- Flash: external 4 MB
- I/O: 26 pins
- Temperature sensor: range of -40°C to 125°C
- Hall sensor
The pinout of the ESP32Dev Board and the Wemos LoLin32 are different.
Let's come to the details:
Supply voltage, analog: 3.3 V
Reference voltage: nominal 1.1 V, span: 1.0 - 1.2 Volt, see here
Offset: the ADC has an offset voltage of 0.1 V.
Voltage Scaling: Espressif tell about attenuation. The highest usable attenuation is 6 dB = divider factor 2. The maximum attenuation is 11 dB (software default), but it is not linear, and needs a lookup table for using it.
See on the right side the picture. The jumper can be replaced with an mA meter for measuring the standby current.
Links #1. Then you need the Hardware Extension ESP32, which can be installed with:
100Pcs Mini Micro JST 2.0 PH 2Pin Connector Plug With 120mm Wires Cables, 3 EUR, https://www.banggood.com Product ID: 1147298
Arduino Software IDE download (Integrated Development Environment), actual version 1.8.5.
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-- RudolfReuter 2018-05-03 18:02:24