NU32: Using the MCP42X1 SPI Digital Potentiometer - Revision history

Lynch at 11:40, 16 January 2016

2016-01-16T11:40:39Z

2012-07-14T20:47:16Z

Details

2012-07-14T20:46:35Z

Details

2012-07-14T18:19:11Z

Sample Code

2012-07-14T18:18:18Z

Details

2012-07-14T18:17:35Z

Sample Code

2012-07-14T18:17:00Z

Sample Code

2012-07-14T18:10:52Z

Library Functions

2012-07-14T18:10:30Z

Library Functions

2012-07-14T17:52:07Z

Overview

← Older revision		Revision as of 11:40, 16 January 2016
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			'''THIS PAGE REFERS TO A PRE-RELEASE VERSION OF THE NU32 PIC32 DEVELOPMENT BOARD. FOR INFORMATION, SAMPLE CODE, AND VIDEOS RELATED TO THE PRODUCTION VERSION (2016 AND LATER), AND TO THE CORRESPONDING BOOK "EMBEDDED COMPUTING AND MECHATRONICS WITH THE PIC32 MICROCONTROLLER," VISIT [[NU32\|THE NU32 PAGE]].'''


	The MCP42X1 is a 7-bit dual digital potentiometer. It is available in total resistance options of 5, 10, 50 and 100 kOhm. It is controlled using SPI communication and a digital output (CS). It has two independent potentiometer channels, each with its own wiper.		The MCP42X1 is a 7-bit dual digital potentiometer. It is available in total resistance options of 5, 10, 50 and 100 kOhm. It is controlled using SPI communication and a digital output (CS). It has two independent potentiometer channels, each with its own wiper.

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 Example schematic when communicating with the NU32, using SPI channel 1:
-* Pot 1-CS        ----->	   F3 (this can be any DIO pin you want, change code accordingly)
+* Pot 1-CS        ----->	   NU32-F3 (this can be any DIO pin you want, change code accordingly)
-* Pot 2-SCK      ----->	   D10
+* Pot 2-SCK      ----->	   NU32-D10
-* Pot 3-SDI       ----->	   D0
+* Pot 3-SDI       ----->	   NU32-D0
 * Pot 4-VSS	----->	   GND
 * Pot 5-P1B	----->       P1+
@@ Line 27: / Line 27: @@
 * Pot 10-P0B    ----->       P0+
 * Pot 12 - SHDN ----->    3.3v (this pin is inverse-shutdown, so we keep it high)
-* Pot 13-SDO  ----->       C4
+* Pot 13-SDO  ----->       NU32-C4
 * Pot 14-VDD  ----->       3.3v

@@ Line 18: / Line 18: @@
 Example schematic when communicating with the NU32, using SPI channel 1:
-* Pot 1-CS        ----->	   F3
+* Pot 1-CS        ----->	   F3 (this can be any DIO pin you want, change code accordingly)
 * Pot 2-SCK      ----->	   D10
 * Pot 3-SDI       ----->	   D0

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 == Sample Code ==
-Initialize and clear the LCD:
+Initialize and manipulate the pots:
 <code><pre>

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 * Pot 5-P1B	----->       P1+
 * Pot 6-P1W	----->       P1-
-* Pot 7-P1A	----->      NC
+* Pot 9-P0W     ----->       P0-
-* Pot 8-P0A     ----->       NC
+* Pot 10-P0B    ----->       P0+
-* Pot 9-P0W    ----->       P0-
-* Pot 10-P0B   ----->       P0+
-* Pot 11 -WP   ----->       NC
 * Pot 12 - SHDN ----->    3.3v (this pin is inverse-shutdown, so we keep it high)
 * Pot 13-SDO  ----->       C4

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    //both now at 0
-    //Setting pots to mid-range (64), or 5 kOhm
+    //Setting pots to mid-range (64), or 1/2 the total resistance
      setPot(0,64);

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 Initialize and clear the LCD:
 <code><pre>
-  LcdInitialize();
-  LcdClear();
+    SPI_initPots();
+    //Setting pots to zero...
+     setPot(0,0);
+     setPot(1,0);
+   //both now at 0
+    //Setting pots to mid-range (64), or 5 kOhm
+     setPot(0,64);
+     setPot(1,64);
+   // both at 64
+    //Incrementing both
+    incPot(0);
+    incPot(1);
+   // (now at 65)
+    //Incrementing both
+    incPot(0);
+    incPot(1);
+   //now at 66
+    //Decrementing both
+    decPot(0);
+    decPot(1);
+   //now 65
+    //Decrementing both
+    decPot(0);
+    decPot(1);
+   //now 64
 </pre></code>

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 Code: [[Media:MCP42X1.h|MCP42X1.h]], [[Media:MCP42X1.c|MCP42X1.c]]
-Full example project: [[Media:MCP42X1_Example.zip]]
+Full example project: [[Media:MCP42X1_Example.zip|MCP42X1_Example.zip]]
 MCP42X1.c contains the following functions:

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 A potentiometer is useful in a variety of circumstances when a variable resistance is needed. A digital potentiometer provides a variable resistor that can be controlled from a microcontroller. Because the MCP42X1 is a 7-bit device, there are 2^7 = 128 possible resistance "steps". By communicating with the IC over SPI, we can choose what step (and thus, resistance) the potentiometer is set at.
-[[File: mcp42x1.png]]
+[[image:mcp42x1.png|thumb|300px|MCP42X1 Pinout|right]]
 The resistance across the PxB and PxW (the wiper) is governed by