GY-63_MS5611/libraries/X9C10X

X9C10X

Arduino Library for X9C10X series digital potentiometer.

Description

This experimental library provides a X9C10X base class and four derived classes for specific digital potentiometer.

type	resistance	tested	notes
X9C10X	generic	Y	base class
X9C102	1 KΩ	N	10 * 10^2
X9C103	10 KΩ	Y	10 * 10^3
X9C104	100 KΩ	N	10 * 10^4
X9C503	50 KΩ	N	50 * 10^3

Note: Ω Ohm sign = ALT-234

The library keeps cache of the position.

PINOUT

//  PINOUT  X9C10X TOP VIEW  (see datasheet)
//
//       +--------+
//  INC  | o    o |  VCC
//  U/D  | o    o |  CS
//  RH   | o    o |  RL
//  GND  | o    o |  Rwiper
//       +--------+
//
//  INC   pulses
//  U/D   UP = 1 DOWN = 0
//  VCC   +5V
//

Interface

X9C10X base class

Use #include "X9C10X.h"

• X9C10X(uint32_t Ohm = 10000) Constructor, default initializes the resistance to 10000 Ω. To calibrate one can fill in any other value e.g. 9950 Ω.
• void begin(uint8_t pulsePin, uint8_t directionPin, uint8_t selectPin, uint8_t position = 0) sets the pins used by the device, and resets the position (default to 0). The position parameter allows to start the device with a previous stored position. Use this position with care.

Note: begin() has a hard coded 500uS delay so the device can wake up.

Note: multiple devices can be controlled, just by giving them an unique selectPin. This behaviour is similar to the SPI select pin.

• void setPosition(uint8_t position, bool forced = false) sets the wiper to a position between 0 and 99. The movement is relative to the current (cached) position. If forced is set to true, the cached position is ignored and the new position will be cached.
• uint8_t getPosition() returns the current position.
• bool incr() moves one position up (if possible). Returns true if moved and false if already at end position.
• bool decr() moves one position down (if possible). Returns true if moved and false if already at end position.
• uint32_t getOhm() returns the position expressed in Ohm. The returned value does depend on the value passed in the constructor.
• uint32_t getMaxOhm() returns the maximum value ( = parameter from constructor).

Store

Warning: use with care.

• uint8_t store() stores the current position in the NVRAM of the device, and returns the current position so it can later be used as position parameter for begin().

If one uses an incorrect parameter position in begin() the internal state and the device will probably be out of sync. One way to sync is call begin() with the right parameters. The other way is to call setPosition(0) followed by setPosition(99) (or vice versa) to get a defined internal state.

Calibration

One can measure the resistance between RH and RL and use this value to set in the constructor. Although the value will not differ much from the datasheet one can get more precise values from the getOhm() function this way.

Derived classes

There are 4 derived classes, each with a other (appropriate) default value for the resistance.

• X9C102(uint32_t Ohm = 1000) idem.
• X9C103(uint32_t Ohm = 10000) idem.
• X9C104(uint32_t Ohm = 100000) idem.
• X9C503(uint32_t Ohm = 50000) idem.

These classes have the same interface as the base class. The only difference is that the type is set.

Performance

The table below is tested on a (relative slow) Arduino UNO 16 MHz with IDE 1.18.19. Other processors might give similar or faster times. See performance example.

X9C10X_LIB_VERSION: 0.1.2

function	time in us	notes
getPosition	4	cached value
setPosition(33)	304	from 0 to 33
setPosition(66)	524	from 0 to 66
setPosition(99)	780	from 0 to 99
setPosition(33)	288	from 0 to 33
setPosition(66)	276	from 33 to 66
setPosition(99)	276	from 66 to 99
setPosition(33)	12	from 33 to 33 = no move
setPosition(66)	4	from 66 to 66 = no move
setPosition(99)	4	from 99 to 99 = no move
getMaxOhm	4	cached value
getOhm()	48
incr()	28.8	average 10 calls
decr()	29.2	average 10 calls

Time per step is 780 / 99 = ~8 us per step on an UNO.

Operation

See examples.

Voltage divider

The digital potentiometer (esp 10 KΩ and up) can be used as a voltage divider. Connect RL to GND and RH to +5V and you can do 5V in 100 steps of ~0.05V A voltage of 3V3 would be setPosition(66).

Note: check datasheet for the range of the max voltage allowed.

Future

• test different platforms
• improve the hardcoded 500us delay in begin()
• add error codes ?
• test store()
• in the constructor rename Ohm parameter to value?
  • The potentiometer can be used as a voltage divider (see above) so a better parameter name could be the anonymous value.
  • getOhm() ==> getValue()
  • getMaxOhm() ==> getMaxValue()
  • think milliVolt, ohm, lux, speed, etc. User can do this too with getPosition()