This is anothe small module to measure air pressure, temperature and humidity. Two sensors are on-board: MS5637 and HDC1080. Microcontroller is small cortex M0 in TSSOP-20 housing from STM: STM32F070CxP. The SN65HVD72DGKR provides RS485 interface functionality with half duplex mode. Voltage regulator, reverse polarity protection and some LED indicators are provided on-board. Complete module is 10x55mm, produced on single-sided PCB, easily producible in every home lab with proto-PCB capability.
Testing of sensors with RS485 using PC without proper interface is not possible. Since RS232 interfaces are very rare, the interface should be hooked to USB. The interface between USB and RS485 can be soldered with one of the many FTDI interfaces with added RS485 driver, or bought as assembled module. There is always the third option. I made it from scratch.
I took smallest STM32F0 with USB and UART interface. The best thing with UART in the STM32F0 is that signal for driver enable is provided within hardware. The complete pinout of the microcontroller is:
The Si7013 I2C Humidity and 2-Zone Temperature Sensor is a monolithic CMOS IC integrating humidity and temperature sensor elements, an analog-to-digital
converter, signal processing, calibration data, and an I2C Interface. The patented use of industry-standard, low-K polymeric dielectrics for sensing humidity enables the construction of low-power, monolithic CMOS Sensor ICs with low drift and hysteresis, and excellent long term stability. The humidity and temperature sensors are factory-calibrated and the calibration data is stored in the on-chip non-volatile memory. This ensures that the sensors are fully interchangeable, with no recalibration or software changes required. An auxiliary sensor input with power management can be tied directly to an external thermistor network or other voltage-output sensor. On-board logic performs calibration/linearization of the external input using user-programmable coefficients. The least-significant bit of the Si7013’s I2C address is programmable, allowing two devices to share the same bus. The Si7013 is available in a 3×3 mm DFN package and is reflow solderable. The
optional factory-installed cover offers a low profile, convenient means of protecting the sensor during assembly (e.g., reflow soldering) and throughout the life of the product, excluding liquids (hydrophobic/oleophobic) and particulates. The Si7013 offers an accurate, low-power, factory-calibrated digital solution ideal for measuring humidity, dew-point, and temperature, in applications ranging from HVAC/R and asset tracking to industrial and consumer platforms.
I prepared prototyping board with STM32F0 and line RS485 driver:
Today I found out how to “flash” blank STM32F103xC to make STLINK V2 debugger interface.
So, instead of desoldering from Discovery board to make miniture STLINK debug interface:
it’s possible to solder blank (or any) STM32F10x with USB and at least 64k flash + 20k RAM, program it with STLINK V2 Firmware and use your new USB dongle for debugging STM32 or STM8 devices.
I am using U-Link from Keil for my debugging purposes. Sometimes it is quite bulky. I decided to design STLink V2 on a single-sided PCB in smallest possible size. Here is how it looks:
This is preliminary preview. I will post more details after first testing.
This is simple, small interface between USB and alphanumeric LCD with 16×2 characters. It is using CDC class – Virtual COM port.
Microcontroller is from STM32 cortex M0 value line family: STM32F070F6. This small “gizmo” has very attractive price and good choice of peripheral devices, like ADC, USB, plenty of timers, etc… Really nice device in “DIY-friendly” package – TSSOP20.
