Analogread function always returning zero

[Joeyapd]

I have some issues with the analog read function of my STM32L082KZ. I have made a custom variants, peripherals file etc. to integrate the board into the PlatformIO environment. In the past (1/2 years ago) it worked perfectly fine but now when i try to use the analogread function it always returns 0. I know for certain it worked with the PA6 pin, but PA 4 and 5 are new pins i want to connect.

I have written a small code to test the functionality:

pinMode(PA4, INPUT);
pinMode(PA5, INPUT);
pinMode(PA6, INPUT);

Serial.print("Digital: “);
Serial.print(digitalRead(PA4));
Serial.print(”, “);
Serial.print(digitalRead(PA5));
Serial.print(”, ");
Serial.println(digitalRead(PA6));
delay(1000);

adcvalue = analogRead(PA4);
Serial.print("Analog: “);
Serial.print(adcvalue);
Serial.print(”, “);
Serial.print(analogRead(PA5));
Serial.print(”, ");
Serial.println(analogRead(PA6));
delay(1000);

This code shows that when using digitalRead the pin does register a voltage but analogread still returns 0.

My variants.cpp file is built as follows:

// Digital PinName array
const PinName digitalPin[] = {
PC_14, // D0
PC_15, // D1
PA_8, // D2
PA_0, // D3 STM32: ADC_IN0
PA_15, // D4 Arduino: SS(D4) STM32: NSS
PA_11, // D5
PA_12, // D6
PA_13, // D7
PA_14, // D8
PB_7, // D9
PA_4, // D10 Arduino: SS1(D10) STM32: NSS / ADC_IN4 / DAC_OUT1
PB_5, // D11 Arduino: MOSI(D11) STM32: MOSI
PB_4, // D12 Arduino: M1S0(D12) STM32: MISO
PB_3, // D13 Arduino: SCK(D13) STM32: SCK
PA_10, // D14 Arduino: SDA(D14) STM32: SDA_1
PA_9, // D15 Arduino: SCL(D15) STM32: SCL_1
PA_1, // D16 STM32: ADC_IN1
PA_2, // D17 STM32: ADC_IN2
PA_3, // D18 STM32: ADC_IN3
PB_6, // D19
PA_5, // D20 STM32: ADC_IN5 / DAC_OUT2
PA_6, // D21 STM32: ADC_IN6
PA_7, // D22 STM32: ADC_IN7
PB_0, // D23 STM32: ADC_IN8 / Vref_OUT
PB_1, // D24 STM32: ADC_IN9 / Vref_OUT
};

// Analog (Ax) pin number array
const uint32_t analogInputPin[] = {
0, // A0, PA0
1, // A1, PA1
2, // A2, PA2
3, // A3, PA3
4, // A4, PA4
5, // A5, PA5
6, // A6, PA6
7, // A7, PA7
16, // A8, PB0
17 // A9, PB1
};

[fpistm]

Your variant .cpp is not correct.
analogInputPin is not correct.
It is also linked to the .h file.
Could you share it.

[Joeyapd]

This is my variants.h file, thanks for the quick reply

/*
 *******************************************************************************
 * Copyright (c) 2020-2021, STMicroelectronics
 * All rights reserved.
 *
 * This software component is licensed by ST under BSD 3-Clause license,
 * the "License"; You may not use this file except in compliance with the
 * License. You may obtain a copy of the License at:
 *                        opensource.org/licenses/BSD-3-Clause
 *
 *******************************************************************************
 */
#pragma once

/*----------------------------------------------------------------------------
 *        STM32 pins numbers my boards
 *----------------------------------------------------------------------------*/
#define PC14  0
#define PC15  1
#define PA8   2
#define PA0   3		//A0
#define PA15  4
#define PA11  5
#define PA12  6
#define PA13  7
#define PA14  8
#define PB7   9
#define PA4  10		//A4
#define PB5  11
#define PB4  12
#define PB3  13
#define PA10 14
#define PA9  15
#define PA1  16		//A1
#define PA2  17		//A2
#define PA3  18		//A3
#define PB6  19
#define PA5  20		//A5
#define PA6  21		//A6
#define PA7  22		//A7
#define PB0  23		//A8
#define PB1  24		//A9

// Alternate pins number
#define PA2_ALT1                (PA2  | ALT1)
#define PA3_ALT1                (PA3  | ALT1)
#define PA6_ALT1                (PA6  | ALT1)
#define PA7_ALT1                (PA7  | ALT1)
#define PA14_ALT1               (PA14 | ALT1)
#define PB4_ALT1                (PB4  | ALT1)
#define PB5_ALT1                (PB5  | ALT1)

#define NUM_DIGITAL_PINS        25
#define NUM_ANALOG_INPUTS       10

// On-board LED pin number
#ifndef LED_BUILTIN
  #define LED_BUILTIN           PNUM_NOT_DEFINED
#endif

// On-board user button
#ifndef USER_BTN
  #define USER_BTN              PNUM_NOT_DEFINED
#endif

// SPI definitions
#ifndef PIN_SPI_SS
  #define PIN_SPI_SS            PA4
#endif
#ifndef PIN_SPI_SS1
  #define PIN_SPI_SS1           PA15
#endif
#ifndef PIN_SPI_SS2
  #define PIN_SPI_SS2           PNUM_NOT_DEFINED
#endif
#ifndef PIN_SPI_SS3
  #define PIN_SPI_SS3           PNUM_NOT_DEFINED
#endif
#ifndef PIN_SPI_MOSI
  #define PIN_SPI_MOSI          PA7
#endif
#ifndef PIN_SPI_MISO
  #define PIN_SPI_MISO          PA6
#endif
#ifndef PIN_SPI_SCK
  #define PIN_SPI_SCK           PA5
#endif

// I2C definitions
#ifndef PIN_WIRE_SDA
  #define PIN_WIRE_SDA          PA10
#endif
#ifndef PIN_WIRE_SCL
  #define PIN_WIRE_SCL          PA9
#endif

// Timer Definitions
// Use TIM6/TIM7 when possible as servo and tone don't need GPIO output pin
#ifndef TIMER_TONE
  #define TIMER_TONE            TIM6
#endif
#ifndef TIMER_SERVO
  #define TIMER_SERVO           TIM7
#endif

// UART Definitions
#ifndef SERIAL_UART_INSTANCE
  #define SERIAL_UART_INSTANCE  0 // 0 for SerialLP1 (LPUART1) (Info: WSerial.h)
#endif

// Default pin used for generic 'Serial' instance
// Mandatory for Firmata
#ifndef PIN_SERIAL_RX
  #define PIN_SERIAL_RX         PA13
#endif
#ifndef PIN_SERIAL_TX
  #define PIN_SERIAL_TX         PA14
#endif

// Extra HAL modules
#if !defined(HAL_DAC_MODULE_DISABLED)
  #define HAL_DAC_MODULE_ENABLED
#endif
#if !defined(HAL_DAC_MODULE_DISABLED)
	#define HAL_RTC_MODULE_ENABLED
#endif

/*----------------------------------------------------------------------------
 *        Arduino objects - C++ only
 *----------------------------------------------------------------------------*/

#ifdef __cplusplus
  // These serial port names are intended to allow libraries and architecture-neutral
  // sketches to automatically default to the correct port name for a particular type
  // of use.  For example, a GPS module would normally connect to SERIAL_PORT_HARDWARE_OPEN,
  // the first hardware serial port whose RX/TX pins are not dedicated to another use.
  //
  // SERIAL_PORT_MONITOR        Port which normally prints to the Arduino Serial Monitor
  //
  // SERIAL_PORT_USBVIRTUAL     Port which is USB virtual serial
  //
  // SERIAL_PORT_LINUXBRIDGE    Port which connects to a Linux system via Bridge library
  //
  // SERIAL_PORT_HARDWARE       Hardware serial port, physical RX & TX pins.
  //
  // SERIAL_PORT_HARDWARE_OPEN  Hardware serial ports which are open for use.  Their RX & TX
  //                            pins are NOT connected to anything by default.
  #ifndef SERIAL_PORT_MONITOR
    #define SERIAL_PORT_MONITOR   Serial
  #endif
  #ifndef SERIAL_PORT_HARDWARE
    #define SERIAL_PORT_HARDWARE  Serial
  #endif
#endif

[fpistm]

So your variant is not correctly defined. Analog pin should be declared using PIN_AX. Check how other variant are defined and also the wiki

[Joeyapd]

Thanks for the answer, this indeed fixed it. But now my digital read after analog read doesn't work anymore, do you know if there is any solution to use the two functions simultaneously? I.E. perform a digital read, wait 1sec, perform an analog read, wait 1sec, perform a digital read etc...

Second question, will it have implications on old BIN files who have been compiled with the wrong variant but do not use the analogue functions of these ports?

[fpistm]

AnalogRead configure itself the pin. While digital Read require to use pinmode before.

For 2nd qurstion. Probably yes.

[Joeyapd]

Do you have any idea what functionality might be impacted or would you recommend reflashing all old firmware that was working and tested in the past?

[fpistm]

If your pin mapping is wrong then you probably use wrong pin or peripheral linked to a pin.