This project exposes the status of connected sensors on a HTTP Webpage & API, using the ChibiOS (master) and lwIP (2.1.x) software stacks.
The hardware components are:
- ST STM32H753ZI ARM Cortex-M7F Development Board - Product Link
/api/status
{"contacts": [{"name": "CH1", "value": 0}], "environmentals": [{"name": "CH2-FAKE", "temperature": 17.60, "humidity": 65.50}]}
This toolchain is designed for Linux.
You must have arm-none-eabi-gcc from GNU ARM embedded toolchain in your path.
Running firmware/build -M will pack the web files and then compile all source files in parallel. The final linker stage can take a few seconds. Running without the -M flag will remove parallel compilation and may help errors to be more readable.
firmware/flash will flash a compiled firmware image. This first looks for a connected BlackMagic JTAG probe, and if unsuccessful will drop back to st-flash from st-utils to flash over the ST-Link USB.
firmware/build -MF will build, and if successful also attempt to flash.
Bootup output can be observed on the USB ACM (Virtual COM Port) shell on the ST-Link connector. The baudrate must be set to 115200.
A USB ACM (Virtual COM Port) shell is provided on the "User USB" micro-USB port for managing the configuration. This can be accessed with screen /dev/ttyACMx or PuTTY on windows. The configured baudrate doesn't matter here.
The configuration routines that save to flash are not suitable for the STM32H7 with it's aggressive caching and so have been disabled. These will be implemented once I get my hands on a SPI FRAM chip to use for the configuration storage.
Currently only a proof-of-concept dry-contact input is configured on pin PC7 (ZIO header pin D21) with internal pull-up to wet a demonstration input contact between PC7 and board GND.
For proper use the Dry Contacts inputs should be used with an opto-isolater to protect the inputs from static discharge and inter-equipment voltage potentials. An isolated DC-DC should also be used for each channel to generate the wetting voltage. Example components would be:
- Lite-On LTV-357T 3750VDC Isolation Optoisolator - Datasheet
- Traco Power TBA 1-0512 5V in, 12V out, 1W, 1000VDC Isolation DC-DC Converter - Product Page
Additional input pins must be configured in firmware/cfg/board.h, and must then be added to the contacts array at the top of firmware/contacts.c.
For the environmental sensors no interface is currently configured, however ChibiOS libraries include a driver for the ST HTS221 Temperature & Humidity Sensor which is commonly available on breakout boards. Sensor Datasheet, ChibiOS Documentation.
Another approach would be to implement a RS-422 multidrop bus, pairing each sensor with an inexpensive microcontroller and PHY to facilitate polling communication, then allowing far greater distances (1km+) between the Hub board and the Sensors.
GPLv3 licensed. © Phil Crump - phil@philcrump.co.uk
Derivations from other license-compatible works are acknowledged in the source.