141 lines
6.9 KiB
Markdown
141 lines
6.9 KiB
Markdown
The LED clock is an add-on for round wall clocks.
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The purpose is to have LEDs on the circumference of the clock to show the progress of the time using coloured light.
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For that you will need:
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- a WS2812B RGB LEDs strip (long enough to go around the clock)
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- a development board with a STM32F103 micro-controller equipped with a 32.768 kHz oscillator for the Real Time Clock (such as the [blue pill](https://wiki.cuvoodoo.info/doku.php?id=stm32f1xx#blue_pill)), or using a external [Maxim DS1307](https://www.maximintegrated.com/en/products/digital/real-time-clocks/DS1307.html) RTC module
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- a coin cell battery to keep the RTC running (optional)
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- a GL5528 photo-resistor to adjust the LED brightness (optional)
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- a DCF77 module to set and update the time automatically (salvaged from a radio controlled digital clock)
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project
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=======
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summary
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-------
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The time will be shown as arc progress bars, in addition to the original hands of the clock pointing at the current time.
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The hours passed since the beginning of the midday are shown using blue LEDs.
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The minutes passed sine the beginning of the hour are shown using green LEDs.
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Whichever progress is higher will be shown on top of the other.
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For example if it's 6:45, the first half of the circle will be blue, and an additional quarter will be green.
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The seconds passed since the beginning of the minute are shown using a running red LED, similar to the seconds hand.
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The red colour might be added on top of the blue, or green colour, then showing as violet or orange.
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The (gamma corrected) brightness of the last LED shows how much of the hour, minute, or second has passed.
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technology
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----------
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The brain of this add-on is a [STM32 F1 series micro-controller](http://www.st.com/web/en/catalog/mmc/FM141/SC1169/SS1031) (based on an ARM Cortex-M3 32-bit processor).
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To keep track of the time a Real Time Clock (RTC) is used.
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If the board includes a 32.768 kHz oscillator (such as a [blue pill](https://wiki.cuvoodoo.info/doku.php?id=stm32f1xx#blue_pill)) the micro-controller will use the internal RTC.
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Otherwise connect an external [Maxim DS1307](https://www.maximintegrated.com/en/products/digital/real-time-clocks/DS1307.html) RTC module to the I2C port and set `EXTERNAL_RTC` in `main.c` to `true`.
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Also connect the external RTC square wave output in order to have a sub-second time precision.
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Connect a DCF77 module (e.g. salvaged from a radio controlled clock) to the micro-controller.
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This will allow to automatically get precise time (at least in Europe) when booting.
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Since the RTC is drifting, the time will get updated using DCF77 every hour to keep <0.5 s time precision.
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Alternatively set the time using serial over the USB port (providing the CDC ACM profile) or USART port and enter "time HH:MM:SS".
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Power the board using an external 5 V power supply (e.g. through the USB port).
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This will power the micro-controller, and the LEDs (a single LED consumes more energy than the micro-controller).
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To keep the correct time in case the main power supply gets disconnected optionally connect a 3 V coin battery on the VBAT pin for the internal RTC, or in the module for the external RTC.
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For the LEDs use a 1 meter LED strip with 60 red-green-blue WS2812B LEDs.
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Tape the LED strip along the border/edge of the clock.
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Ideally the wall clock has a diameter of 32 cm for a 1 m LED strip to completely fit.
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Otherwise change the number of actually used LEDs in the source files.
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Connect the 5 V power rail of the LED strip to the 5 V pin of the board.
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Connect the DIN signal line of the LED strip to the MISO pin of the micro-controller on PA6.
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SPI is used to efficiently shift out the LED colour values to the WS2812B LEDs.
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A custom clock is provided for this operation using channel 3 of timer 3 on pin PB0.
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Simply connect this clock to the SPI CLK input on pin PA5.
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The brightness of the LEDs is dependant on the ambient luminance.
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To measure the ambient luminance a GL5528 photo-resistor is used.
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Connect one leg of the photo-resistor to ADC channel 1 and the other to ground.
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Connect one leg of a 1 kOhm resistor to ADC channel 1 and the other to a 3.3 V pin.
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This voltage divider allows to measure the photo-sensor's resistance and determine the luminance.
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If you don't want to use this feature, connect PA1 to ground for the highest brightness or Vcc for the lowest brightness.
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board
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=====
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The current implementation uses a [blue pill](https://wiki.cuvoodoo.info/doku.php?id=stm32f1xx#blue_pill).
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The underlying template also supports following board:
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- [Maple Mini](http://leaflabs.com/docs/hardware/maple-mini.html), based on a STM32F103CBT6
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- [System Board](https://wiki.cuvoodoo.info/doku.php?id=stm32f1xx#system_board), based on a STM32F103C8T6
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- [blue pill](ihttps://wiki.cuvoodoo.info/doku.php?id=stm32f1xx#blue_pill), based on a STM32F103C8T6
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**Which board is used is defined in the Makefile**.
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This is required:
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- for the linker script to know the memory layout (flash and RAM)
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- map the user LED and button provided on the board
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connections
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===========
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Connect the peripherals the following way (STM32F10X signal; STM32F10X pin; peripheral pin; peripheral signal; comment):
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- USART1_TX; PA9; RX; UART RX; optional, same as over USB ACM
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- USART1_RX; PA10; TX; UART TX; optional, same as over USB ACM
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- I2C1_SDA; PB7; DS1307 SDA; SDA; optional, when using external RTC
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- I2C1_SCL; PB6; DS1307 SCL; SCL; optional, when using external RTC
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- TIM2_CH1_ETR; PA0; DS1307 SQ; square wave output; optional, when using external RTC
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- ADC12_IN1; PA1; GL5528; photo-resistor + 1 kOhm to 3.3 V; without GL5528 photo-resistor connect to ground for highest brightness or Vcc for lowest brightness
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- TIM3_CH3; PB0; PA5; SPI1_SCK; generated clock for WS2812B transmission
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- SPI1_MISO; PA6; WS2812B DIN; DIN; WS2812B LED strip data stream
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- GPIO; PA2; DCF77 PO; \#EN; DCF77 enable on low
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- GPIO; PA3; DCF77 TN; DCF77; DCF77 high bit pulses
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All pins are configured using `define`s in the corresponding source code.
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code
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====
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dependencies
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------------
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The source code uses the [libopencm3](http://libopencm3.org/) library.
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The projects is already a git submodules.
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To initialize and it you just need to run once: `git submodule init` and `git submodule update`.
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firmware
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--------
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To compile the firmware run `make`.
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documentation
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-------------
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To generate doxygen documentation run `make doc`.
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flash
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-----
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The firmware will be flashed using SWD (Serial Wire Debug).
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For that you need an SWD adapter.
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The `Makefile` uses a ST-Link V2 along OpenOCD software (per default), or a Black Magic Probe.
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To flash using SWD run `make flash`.
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debug
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-----
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SWD also allows to debug the code running on the micro-controller using GDB.
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To start the debugging session run `make debug`.
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USB
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---
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The firmware offers serial communication over USART1 and USB (using the CDC ACM device class).
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You can also reset the board by setting the serial width to 5 bits over USB.
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To reset the board run `make reset`.
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This only works if the USB CDC ACM is running correctly and the micro-controller isn't stuck.
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