SDI/SDO multiplexing with MCP4161

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hi,

i'm trying hook 2 mcp4161 digital potentiometers arduino uno. i'm using example mcp4261 found here: https://github.com/teabot/mcpdigitalpot

now, mcp4261 used in example has sdi , sdo on separate pins, connected pins 11 , 12 on arduino. mcp4161 has sdi , sdo multiplexed on 1 pin. since i'm beginner, don't know how hook up. tried looking in datasheet , on web instructions, didn't find specific. found out resistor has used. can please tell me how determine resistor size need , how connect it?

edit: there wiring diagram in datasheet showing how done, connecting sdi/sdo pin on chip sdi pin on arduino directly, , sdo pin on arduino via resistor. not specify correct value resistor, says must sized ensure vil , vih of device. according datasheet, these schmitt trigger low , high thresholds. don't know how determine these though. found page: http://www.sparkfun.com/products/10613 mentioned 4.7 kohm resistor used. if no-one has better advice, try hooking size , see if can working.

do need read pot?  if not don't need resistor @ all.

however if @ fig 6-1 in data sheet shows 3 ways hook up, second option need, resistor goes between mosi , miso pins (shown sdo , sdi on host controller).

quote
it says must sized ensure vil , vih of device.

i think have stop current flowing in case of level clash, 470r or 1k should ok.

i must looks complicated chip if need simple pot though.

______
rob


Arduino Forum > Using Arduino > LEDs and Multiplexing > SDI/SDO multiplexing with MCP4161


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