PICAXE Manual Section 1 - TechnoPujades - Free

www.picaxe.co.ukSection 1 37GETTING STARTEDSerial Download CircuitThe serial download circuit is identical for all PICAXE chips. It consists of 3 wiresfrom the PICAXE chip to the AXE026 serial cable. One wire sends data from thecomputer to the serial input of the PICAXE, one wire transmits data from theserial output of the PICAXE to the computer, and the third wire provides acommon ground. See the USB adapter section for details on how to use the USBport adapter.The minimum download circuit is shown here. This circuit is appropriate formost educational and hobbyist work.abcAbove viewxxcxxxab10k22kserial outserial in0VPICAXE22kserial outserial in0V12312310kPICAXE2. to PICAXE serial out3. to PICAXE serial in5. to PICAXE 0VComputer9 Way D female socketNote that the two resistors are not a potential divider. The 22k resistor works withthe internal microcontroller diodes to clamp the serial voltage to the PICAXEsupply voltage and to limit the download current to an acceptable limit. The 10kresistor stops the serial input ‘floating’ whilst the download cable is notconnected. This is essential for reliable operation.The two download resistors must be included on every PICAXE circuit (i.e. notbuilt into the cable). The serial input must never be left unconnected. If it is leftunconnected the serial input will ‘float’ high or low and will cause unreliableoperation, as the PICAXE chip will receive spurious floating signals which it mayinterpret as a new download attempt.revolution(c) Revolution Education Ltd. Email: info@rev-ed.co.uk Web: www.rev-ed.co.ukVersion 6.9 07/2009All rights reserved.37