MCP401X-STM32-Library-mcp4017-4018-4019-

Library and example to interface MCP401X series (MCP4017/4018/4019) digital potentiometers

Getting Started

Connection Diagram

Tested with NUCLEO-L433RC-P (STM32L433RCT6PU) on MCP4017 and MCP4018.

• Vcc = 3.3V

Sl No	STM32	MCP401X
1	3.3V	1
2	GND	2
3	SCL/D15(PB8)	3
4	SDA/D14(PB7)	4

Measuring Resistance will depend on which MCP401X IC is being used. MCP4017 and MCP4019 are Rheostats, MCP4018 is a Potentiometer. Check Datasheet for pinouts.

I have used the internal pullups of STM32 for I2C

Folder Structure

.
├── Images
├── Workspace 						# STM32CubeIDE Workspace          
│   └── MCP401X-Interface 				# Project
│   	├── Core         
│   	│   ├── Inc 					# Header files
│   	│   ├── Src 					# Source files 
│   	│   └── Startup
│   	├── Debug 					# Binary files 
│   	├── Drivers 
│   	├── .cproject 
│   	├── .mxproject 
│   	├── .project 
│   	├── MCP401X-Interface Debug.launch 
│   	├── MCP401X-Interface.ioc 			# CubeMX file
│   	└── STM32L433RCTXP_FLASH.ld		
├── examples                		 	
│   └── main.c 						# example main.c
├── LICENSE              			
├── README.md             			
├── mcp401x.c 						# Library source file 
└── mcp401x.h 						# Library header file 

Usage

main.c

Include the header file #include "mcp401x.h" in main.c

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "mcp401x.h"
/* USER CODE END Includes */

Usage example of main.c

uint8_t stepBuf[3] = {0, 64, 127};
uint8_t step = 0;
uint32_t Rwb;

SetStep(&stepBuf[0]);			//Set Min value Resistance
step = ReadStep();
//	HAL_Delay(5000);

SetStep(&stepBuf[1]);			//Set Middle value Resistance
step = ReadStep();
//  HAL_Delay(5000);

SetStep(&stepBuf[2]);			//Set Max value Resistance
step = ReadStep();
//	HAL_Delay(5000);

SetResistance(2500);			//Set Resistance value 2.5K
step = ReadStep();				//Read the step value
Rwb = ReadResistance();			//Read the Resistance value from chip
//	HAL_Delay(5000);

If you are using ST-Link/J-link to debug, use break points to see the value change, otherwise uncomment the HAL_Delay() function.

mcp401x.h

I am using the STM32L4 series,

#include "stm32l4xx_hal.h"					//Change here acc to STM32 series used

If another STM32 series IC is used, include the appropriate header. For example if F1 series (like STM32F103C8T6) is used, replace with below

#include "stm32f1xx_hal.h"					//Change here acc to STM32 series used

Change Resistance value according to the MCP401X IC used. If a 5K Pot is being used, change below value to 5000

#define MAXRESISTANCE    	10000     		//Change here acc to Value of MCP401X

mcp401x.c

Change Handletype acc to I2C used. Here I am using I2C1.

extern I2C_HandleTypeDef hi2c1;

Function used to set step value. Change handletype acc to I2C used. If needed use custom timeout instead of HAL_MAX_DELAY

/**
  * @brief  Set step value. Range 0 - 127
  * @retval None
  */
void SetStep(uint8_t *step)
{
	HAL_I2C_Master_Transmit(&hi2c1, MCP401XADDR, step, 1, HAL_MAX_DELAY);
}

Function used to read step value. Change handletype acc to I2C used. If needed use custom timeout instead of HAL_MAX_DELAY

/**
  * @brief  Read step value. Range 0 - 127
  * @retval int
  */
int ReadStep(void)
{
	uint8_t tempBuf[1] = {0};
	HAL_I2C_Master_Receive(&hi2c1, MCP401XADDR, tempBuf, 1, HAL_MAX_DELAY);
	return *tempBuf;
}

Function used to set Resistance value.

/**
  * @brief  Set Resistance value, Rwb.
  * @retval None
  */
void SetResistance(uint32_t Rwb)
{
	uint8_t step = (((MAXSTEP * Rwb) / MAXRESISTANCE) + (Rwb / 1000));
	if(step > 127)
	{
		step = 127;
	}
	SetStep(&step);
}

Links to Hardware used

• NUCLEO-L433RC-P Board - https://www.st.com/en/evaluation-tools/nucleo-l433rc-p.html
• SC70-6 TO DIP-6 SMT Adapter - https://www.digikey.com/en/products/detail/chip-quik-inc/PA0087/5014718
• MCP4017T-502E/LT - https://www.digikey.com/en/products/detail/microchip-technology/MCP4017T-502E-LT/2059659
• MCP4018T-103E/LT - https://www.digikey.com/en/products/detail/microchip-technology/MCP4018T-103E-LT/2059661