17-12-2012, 04:50 PM
T-Clock
T-Clock.docx (Size: 30.13 KB / Downloads: 33)
The "T-Clock" (name from the "flipped" T-Shape, not from the T in Thomas ;-) ) demonstrates interfacing a Philips LPC2000-ARM7TDMI with:
Graphics-LCD with KS0107/0108 controller
Contrast and Brightness of LCD controlled by Software (Hardware-PWM)
DCF77 receiver (standard time broadcasted by the PTB)
Onewire-Interface to Maxim/Dallas Temperature-Sensors (DS18x20)
Rotrary Encoder for GUI
Internal controller flash-memory to store configuration-values (contrast/brightness) using IAP
UART in "interrupt-mode" for status-output
The time and date are received with a DCF77-receiver-module (available i.e. from elv.de and conrad.com, ca. 10 EUR). The DCF77-signal is transmitted from a station near Frankfurt/Main, Germany and can be received all over Europe, North Africa and the Middle-East. Please visit www.ptb.de and ask google with "DCF77" for more information. In times when the DCF77-signal is not available (i.e. thunder and lightning near transmitter) the RTC of the LPC-controller is used to drive the clock.
A temperature-sensor from the DS18x20 family by Maxim/Dallas is used. The sensors provide the temperature in digital form on a One-Wire-Bus. The Maxim Web-Site has a lot of information on the One-Wire-Bus.
"Human-Interface" is a 128 by 64 dots graphics LCD with a KS0107/KS0108 combi, an (mechanical rotary) encoder and a single button ("enter"). Brightness and contrast of the GLCD are controlled by software (PWM) with an OP-AMP-based amplifier and inverter circuit. If your GLCD does not provide negative voltage (VEE pin) you may have to use a extra "charge-pump-IC" or a "spare TX" of a MAX232 to get a negative contrast voltage and negative supply for the OP-AMPs.