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Miniature PCM Remote Control 2

the software protocol

Miniature PCM Remote Control 2
In this second and final part of the remote control design we put it all together and take a closer look at the workings of the transmitter and receiver software.As with any communication system it is necessary to decide on a suitable message format to convey the information. This system does not need to comply with any existing communication standard so we are free to design our own. The main objectives are to enable a high data rate together with good reliability and error detection. The specification of the transmitters and receivers must also be considered to ensure, for example, we do not exceed the maximum clock rate or channel bandwidth. With these constraints in mind a message protocol is used (Figure 1) that is suitable for transmission using either IR or RF.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Transmitter
Resistors:
R1 = 470Ohm
R2,R3 = 18kOhm
R3 = 10kOhm
R4 = 1kOhm
R5 = 10Ohm
R6 = 100kOhm
P1-P4 = potentiometer, 20kOhm , linear
P5-P8 = joystick (CTS # 252A104A60TB with internal switch)
Capacitors:
C1 = 220µ F 16V
C2,C3 = 15pF
Semiconductors:
D1 = TSUS5201 or LD271
D2 = LED, red, 3mm
T1 = ZTX603 (Zetex) or TIP110
IC1 = 87LPC768FN, programmed, order code 010205-41
Miscellaneous:
X1 = 6MHz quartz crystal
S3 = on/off switch, 1 make contact
S4 = 4-way DIP switch
JP1 = 2-way pinheader with jumper
UT1 = 433MHz transmitter module type TX2 from Radiometrix (Farnell)
Battery holder for 3 AA cells
PCB, order code 010205-1
Receiver
Resistors:
R1 = 470Ohm
R2,R9 =27kOhm
R3,R8 = 10kOhm
R4 = 100Ohm
R5,R6,R7 = 100kOhm
Capacitors:
C1,C2 = 15pF
C3 = 10µ F 16V
C4,C6 = 100nF
C5 = 470µ F 16V
C7 = 220µ F 16V
Semiconductors:
D1 = LED, red, 3mm
D2 = MBR745
T1 = SUP75N03, IRL2203
T2,T3 = BUZ11
T4 = IRF4905L (International Rectifier)
T5 = BC547
IC1 = 87LPC762BN, programmed, order code 010205-42
IC2 = SFH5110-36 (Siemens)
IC3 = LM2940
Miscellaneous:
X1 = 6MHz quartz crystal
S1 = on/off switch, 1 make contact
JP1,JP2 = 2-way pinheader with jumper
4 servo connector plugs, 3-way
UR1 = 433MHz RX2 receiver module from Radiometrix (Farnell)
PCB, order code 010205-2
Disk, project software, order code 010205-11
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