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fix clock frequency documentation

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King Kévin 2016-04-04 20:04:06 +02:00
parent a8b37de546
commit 3439c2d7ed
1 changed files with 2 additions and 2 deletions
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README.md
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@ -21,7 +21,7 @@ technology
----------
The LEDs are controlled using 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).
The board needs to include a 32.678 kHz oscillator for the Real-Time-Clock (RTC).
The board needs to include a 32.768 kHz oscillator for the Real-Time-Clock (RTC).
Preferably use a [blue pill](https://wiki.cuvoodoo.info/doku.php?id=stm32f1xx#blue_pill) board.
The board needs to be powered by an external 5 V power supply (e.g. using the USB port).
To set the time connect using serial over the USB port (providing the CDC ACM profile) or USART1 port (TX and RX are on pin PA9 and PA10) and enter "time HH:MM:SS".
@ -43,7 +43,7 @@ To measure the ambient luminosity a 5528 photo-resistor is used.
Connect one leg of the photo-resistor to ADC channel 0 on pin PA0 and the other to ground.
Connect one leg of a 1 kOhm resistor to ADC channel 0 on pin PA0 and the other to a 3.3 V pin.
If the board does not provide a 32.678 kHz oscillator for the internal RTC it is also possible to use an external RTC such as the Maxim DS1307.
If the board does not provide a 32.768 kHz oscillator for the internal RTC it is also possible to use an external RTC such as the Maxim DS1307.
The time is then read over I2C and incremented using the square wave output.
Working example code is under the `DS1307_4096Hz_timer` tag.