| Wireless Radio Data Transfer with TX433 & RX433 |
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Wireless data transfer with these cheap modules from Velleman / QualityKits. This first prototype uses two breadboards. One sending and one receiving. My aim was to achieve a protocol with which transmitting & receiving data is pretty much reliable. The future setup will have full two-way communication with CRC and adjusting baud rates if needed. |
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| All parts are available in our online shop |
TX433 |
RX433 |
Okay, here's the first fully working setup:
One sending circuit which transmits the current time (from an i²c real time clock.) It sends 20 bytes in 50 to 70 mS. See waveforms below.
One receiving circuit. Displays the current time received from transmitter. Around 2 readings are made per second.
Range of this setup is around 30 meters indoors and 200 meters outdoors. More about the RTC part here.
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Data transmission waveforms:
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This is how the received signal looks like. "0" is on top of the curve; "1" is at the bottom. The sample is 5mS long. The first signal going high is "transmission start" followed by "new byte" then 8 data bits (=first ID byte with value 0xaa) and then again a "new byte" Oscilloscope 2.51 takes the LINE IN from a soundcard as a 2-channel input.
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Schematics: right-click & "save picture as" for full resolution or download the eagle-file below.
Parts list (Bill of mateterials.)
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Transmitter: |
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| Parts list (Bill of mateterials.) |
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Receiver: |
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Downloads:
WARNING: may not be duplicated for any commercial use whatsoever without explicit consent from the author.
TechDesign Electronics (c) Michel Bavin.
Hex files:
005_v4_TX_hex.zip, October 2, 2003: tx4.hex (to program the PIC)
005_v4_RX_hex.zip, October 2, 2003: rx4.hex (to program the PIC)
ascii_eeprom_v2.zip, September 10, 2003: ascii_eeprom_v2.hex (for the EEPROM.)
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Source code:
005_v4_TX_c.zip (Hi-Tech PICC), October 2, 2003: tx4.c , with include files defs.h, delay.c, delay.h
005_v4_RX_c.zip (Hi-Tech PICC), October 2, 2003: rx4.c , with include files defs.h, delay.c, delay.h
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Schematics:
005_tx_sch.zip (Eagle), October 2, 2003.
005_rx_sch.zip (Eagle), October 2, 2003.
Source code explanation: (Hi-Tech PICC)
TX 433 & RX 433 routines coming soon!!
DS1307: void rtc_read(unsigned char *rtc_buffer): read routine for the DS1307.
i²c EEPROM to NOKIA: void ext_eeprom_to_nokialcd(void): read character en symbol data in eeprom & send them to the NOKIA LCD.
Tools:
I work with the Hi-tech PICC compiler. It is relatively easy to use AND has a complete working FREE version (PICC Lite) available. This lite version is limited to 2K for the 16F877 (1/4 of total code size) but this is sufficient for this projects. You'll have to install Microchip's free MPLAB IDE to get things going.
Programming of the PIC was done with IC-Prog on a PIC- programmer built from Electronique pratique nr 253 (january 2001).
Eagle was used for the PCB layout. The free version was ok for this design. Best is to download the schematic below and then to create your own board.
Info & datasheet:
Graphic LCD module type LPH7779 (NOKIA 3310 LCD) and its integrated controller PCD8544.
