File content as of revision 2:70f92ce7d983:

#include "mbed.h"
/*
 * HAL_TIM_Encoder_MspInit()
 * Overrides the __weak function stub in stm32f4xx_hal_tim.h
 *
 * Edit the below for your preferred pin wiring & pullup/down
 * I have encoder common at 3V3, using GPIO_PULLDOWN on inputs.
 * Encoder A&B outputs connected directly to GPIOs.
 *
 */
 // STM32 F4 HAL https://github.com/mbedmicro/mbed/blob/03fff9249b0ca5efb2e12506ce8fb3e6cc258d9d/libraries/mbed/targets/cmsis/TARGET_STM/TARGET_STM32F4/stm32f4xx_hal_tim.h

#ifdef TARGET_STM32F4
void HAL_TIM_Encoder_MspInit(TIM_HandleTypeDef *htim)
{
    GPIO_InitTypeDef GPIO_InitStruct;

    if (htim->Instance == TIM1) { //PA8 PA9 = Nucleo D7 D8, poss PB0 PB1 usable too (complementary?)
        __TIM1_CLK_ENABLE();
        __GPIOA_CLK_ENABLE();
        GPIO_InitStruct.Pin = GPIO_PIN_8;// | GPIO_PIN_9;   //test one pin for now without direction
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Pull = GPIO_PULLDOWN;
        GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
        GPIO_InitStruct.Alternate = GPIO_AF1_TIM1;
        HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
    }
    else if (htim->Instance == TIM2) { //PA0 PA1 = Nucleo A0 A1, PA5 PB3 = D13 D3 poss too
        __TIM2_CLK_ENABLE();
        __GPIOA_CLK_ENABLE();
        GPIO_InitStruct.Pin = GPIO_PIN_0 | GPIO_PIN_1;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Pull = GPIO_PULLDOWN;
        GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
        GPIO_InitStruct.Alternate = GPIO_AF1_TIM2;
        HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
    }
    else if (htim->Instance == TIM3) { //PB4 PB5 = Nucleo D5 D4, PA6 PA7 & PC6 PC7 also an option for Nucleo
        __TIM3_CLK_ENABLE();
        __GPIOB_CLK_ENABLE();
        GPIO_InitStruct.Pin = GPIO_PIN_4 | GPIO_PIN_5;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Pull = GPIO_PULLDOWN;
        GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
        GPIO_InitStruct.Alternate = GPIO_AF2_TIM3;
        HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
    }
    else if (htim->Instance == TIM4) { // PB6 PB7 = Nucleo D10 MORPHO_PB7
        __TIM4_CLK_ENABLE();
        __GPIOB_CLK_ENABLE();
        GPIO_InitStruct.Pin = GPIO_PIN_6 | GPIO_PIN_7;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Pull = GPIO_PULLDOWN;
        GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
        GPIO_InitStruct.Alternate = GPIO_AF2_TIM4;
        HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
    }
    else if (htim->Instance == TIM5) { // here for completeness, mbed sytem timer uses this
        __TIM5_CLK_ENABLE();
        __GPIOA_CLK_ENABLE();
        GPIO_InitStruct.Pin = GPIO_PIN_0 | GPIO_PIN_1;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Pull = GPIO_PULLDOWN;
        GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
        GPIO_InitStruct.Alternate = GPIO_AF2_TIM5;
        HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
    }
}
#endif