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authorDimitri Sokolyuk <demon@dim13.org>2010-01-06 17:55:16 +0000
committerDimitri Sokolyuk <demon@dim13.org>2010-01-06 17:55:16 +0000
commit09381c6097773b08622c810428a84840b5b08070 (patch)
treef62afce58620ebbffe6abcf1b8e1d8df6a09a5b8 /dongle.txt
AVR SP12 programmer
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+The `dongle' shown here (dongle.gif) was designed by Ken Huntington
+(kenh@compmore.net). It is perhaps unique in not `protecting' a
+copyright, being perfectly transparent to the sp12 software - so you
+can still use a plain cable with this version. And the dongle has no
+power requirements; the 74HC126 receives its Vcc from the port. Yet
+it significantly improves the signal quality. The Sck termination
+(as shown in progrmmr.pdf and icp_intr.pdf) becomes superfluous when
+using it. Some parallel ports won't reliably communicate with an AVR
+uC without it. Moreover, the programming lines are high-Z except
+when sp12 is active.
+
+Apart from powering the dongle, your parallel port will also still
+be able to provide power for a small target board (Icc up to about
+5 mA). When using external power, the high-Z lines make the order of
+switch-on and connection less critical. You can switch on the target
+board first and then connect it to the PC, or make the connection
+and switch it on afterwards. But do make sure that your board resets
+properly! The absolute minimal `reset circuit' is a resistor of
+about 10K between Vcc and the uC's reset pin.
+
+A pcb layout for the dongle can be found on the sp12 Web page:
+
+ http://www.xs4all.nl/~sbolt/e-spider_prog.html
+
+There are also photo's of our prototypes. A 74HC126 is preferred,
+but the dongle does seem to work well enough with a 74HCT126, if the
+parallel port provides a reasonable Vcc value.