docs/adding_features_to_qmk.md


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# How To Add Features To QMK

If you have an idea for a custom feature or extra hardware connection, we'd love to accept it into QMK! 

Before you put a lot of work into building your new feature you should make sure you are implementing it in the best way. You can get a basic understanding of QMK by reading [Understaning QMK](understanding_qmk.html), which will take you on a tour of the QMK program flow. From here you should talk to us to get a sense of the best way to implement your idea. There are two main ways to do this:

* [Chat on Gitter](https://gitter.im/qmk/qmk_firmware)
* [Open an Issue](https://github.com/qmk/qmk_firmware/issues/new)

Once you have implemented your new feature you will generally submit a [pull request](https://github.com/qmk/qmk_firmware/pulls). Here are some things to keep in mind when creating one:

* **Disabled by default** - memory is a pretty limited on most chips QMK supports, and it's important that current keymaps aren't broken, so please allow your feature to be turned **on**, rather than being turned off. If you think it should be on by default, or reduces the size of the code, please talk with us about it.
* **Compile locally before submitting** - hopefully this one is obvious, but things need to compile! Our Travis system will catch any issues, but it's generally faster for you to compile a few keyboards locally instead of waiting for the results to come back.
* **Consider subprojects and different chip-bases** - there are several keyboards that have subprojects that allow for slightly different configurations, and even different chip-bases. Try to make a feature supported in ARM and AVR, or automatically disabled on platforms it doesn't work on.
* **Explain your feature** - Document it in `docs/`, either as a new file or as part of an existing file. If you don't document it other people won't be able to benefit from your hard work.
* **Don't refactor code** - to maintain a clear vision of how things are laid out in QMK, we try to plan out refactors in-depth, and have a collaborator make the changes. If you have an idea for refactoring, or suggestions, [open an issue](https://github.com/qmk/qmk_firmware/issues), we'd love to talk about how QMK can be improved.
/*
    ChibiOS/RT - Copyright (C) 2006-2013 Giovanni Di Sirio

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

/**
 * @file    STM32L1xx/stm32_dma.h
 * @brief   DMA helper driver header.
 * @note    This file requires definitions from the ST header file stm32l1xx.h.
 * @note    This driver uses the new naming convention used for the STM32F2xx
 *          so the "DMA channels" are referred as "DMA streams".
 *
 * @addtogroup STM32L1xx_DMA
 * @{
 */

#ifndef _STM32_DMA_H_
#define _STM32_DMA_H_

/*===========================================================================*/
/* Driver constants.                                                         */
/*===========================================================================*/

/**
 * @brief   Total number of DMA streams.
 * @note    This is the total number of streams among all the DMA units.
 */
#define STM32_DMA_STREAMS           7

/**
 * @brief   Mask of the ISR bits passed to the DMA callback functions.
 */
#define STM32_DMA_ISR_MASK          0x0F

/**
 * @brief   Returns the channel associated to the specified stream.
 *
 * @param[in] n         the stream number (0...STM32_DMA_STREAMS-1)
 * @param[in] c         a stream/channel association word, one channel per
 *                      nibble, not associated channels must be set to 0xF
 * @return              Always zero, in this platform there is no dynamic
 *                      association between streams and channels.
 */
#define STM32_DMA_GETCHANNEL(n, c)  0

/**
 * @brief   Checks if a DMA priority is within the valid range.
 * @param[in] prio      DMA priority
 *
 * @retval              The check result.
 * @retval FALSE        invalid DMA priority.
 * @retval TRUE         correct DMA priority.
 */
#define STM32_DMA_IS_VALID_PRIORITY(prio) (((prio) >= 0) && ((prio) <= 3))

/**
 * @brief   Returns an unique numeric identifier for a DMA stream.
 *
 * @param[in] dma       the DMA unit number
 * @param[in] stream    the stream number
 * @return              An unique numeric stream identifier.
 */
#define STM32_DMA_STREAM_ID(dma, stream) ((stream) - 1)

/**
 * @brief   Returns a DMA stream identifier mask.
 *
 *
 * @param[in] dma       the DMA unit number
 * @param[in] stream    the stream number
 * @return              A DMA stream identifier mask.
 */
#define STM32_DMA_STREAM_ID_MSK(dma, stream)                                \
  (1 << STM32_DMA_STREAM_ID(dma, stream))

/**
 * @brief   Checks if a DMA stream unique identifier belongs to a mask.
 * @param[in] id        the stream numeric identifier
 * @param[in] mask      the stream numeric identifiers mask
 *
 * @retval              The check result.
 * @retval FALSE        id does not belong to the mask.
 * @retval TRUE         id belongs to the mask.
 */
#define STM32_DMA_IS_VALID_ID(id, mask) (((1 << (id)) & (mask)))

/**
 * @name    DMA streams identifiers
 * @{
 */
/**
 * @brief   Returns a pointer to a stm32_dma_stream_t structure.
 *
 * @param[in] id        the stream numeric identifier
 * @return              A pointer to the stm32_dma_stream_t constant structure
 *                      associated to the DMA stream.
 */
#define STM32_DMA_STREAM(id)        (&_stm32_dma_streams[id])

#define STM32_DMA1_STREAM1          STM32_DMA_STREAM(0)
#define STM32_DMA1_STREAM2          STM32_DMA_STREAM(1)
#define STM32_DMA1_STREAM3          STM32_DMA_STREAM(2)
#define STM32_DMA1_STREAM4          STM32_DMA_STREAM(3)
#define STM32_DMA1_STREAM5          STM32_DMA_STREAM(4)
#define STM32_DMA1_STREAM6          STM32_DMA_STREAM(5)
#define STM32_DMA1_STREAM7          STM32_DMA_STREAM(6)
/** @} */

/**
 * @name    CR register constants common to all DMA types
 * @{
 */
#define STM32_DMA_CR_EN             DMA_CCR1_EN
#define STM32_DMA_CR_TEIE           DMA_CCR1_TEIE
#define STM32_DMA_CR_HTIE           DMA_CCR1_HTIE
#define STM32_DMA_CR_TCIE           DMA_CCR1_TCIE
#define STM32_DMA_CR_DIR_MASK       (DMA_CCR1_DIR | DMA_CCR1_MEM2MEM)
#define STM32_DMA_CR_DIR_P2M        0
#define STM32_DMA_CR_DIR_M2P        DMA_CCR1_DIR
#define STM32_DMA_CR_DIR_M2M        DMA_CCR1_MEM2MEM
#define STM32_DMA_CR_CIRC           DMA_CCR1_CIRC
#define STM32_DMA_CR_PINC           DMA_CCR1_PINC
#define STM32_DMA_CR_MINC           DMA_CCR1_MINC
#define STM32_DMA_CR_PSIZE_MASK     DMA_CCR1_PSIZE
#define STM32_DMA_CR_PSIZE_BYTE     0
#define STM32_DMA_CR_PSIZE_HWORD    DMA_CCR1_PSIZE_0
#define STM32_DMA_CR_PSIZE_WORD     DMA_CCR1_PSIZE_1
#define STM32_DMA_CR_MSIZE_MASK     DMA_CCR1_MSIZE
#define STM32_DMA_CR_MSIZE_BYTE     0
#define STM32_DMA_CR_MSIZE_HWORD    DMA_CCR1_MSIZE_0
#define STM32_DMA_CR_MSIZE_WORD     DMA_CCR1_MSIZE_1
#define STM32_DMA_CR_SIZE_MASK      (STM32_DMA_CR_PSIZE_MASK |              \
                                     STM32_DMA_CR_MSIZE_MASK)
#define STM32_DMA_CR_PL_MASK        DMA_CCR1_PL
#define STM32_DMA_CR_PL(n)          ((n) << 12)
/** @} */

/**
 * @name    CR register constants only found in enhanced DMA
 * @{
 */
#define STM32_DMA_CR_DMEIE          0   /**< @brief Ignored by normal DMA.  */
#define STM32_DMA_CR_CHSEL_MASK     0   /**< @brief Ignored by normal DMA.  */
#define STM32_DMA_CR_CHSEL(n)       0   /**< @brief Ignored by normal DMA.  */
/** @} */

/**
 * @name    Status flags passed to the ISR callbacks
 * @{
 */
#define STM32_DMA_ISR_FEIF          0
#define STM32_DMA_ISR_DMEIF         0
#define STM32_DMA_ISR_TEIF          DMA_ISR_TEIF1
#define STM32_DMA_ISR_HTIF          DMA_ISR_HTIF1
#define STM32_DMA_ISR_TCIF          DMA_ISR_TCIF1
/** @} */

/*===========================================================================*/
/* Driver pre-compile time settings.                                         */
/*===========================================================================*/

/*===========================================================================*/
/* Derived constants and error checks.                                       */
/*===========================================================================*/

/*===========================================================================*/
/* Driver data structures and types.                                         */
/*===========================================================================*/

/**
 * @brief   STM32 DMA stream descriptor structure.
 */
typedef struct {
  DMA_Channel_TypeDef   *channel;       /**< @brief Associated DMA channel. */
  volatile uint32_t     *ifcr;          /**< @brief Associated IFCR reg.    */
  uint8_t               ishift;         /**< @brief Bits offset in xIFCR
                                             register.                      */
  uint8_t               selfindex;      /**< @brief Index to self in array. */
  uint8_t               vector;         /**< @brief Associated IRQ vector.  */
} stm32_dma_stream_t;

/**
 * @brief   STM32 DMA ISR function type.
 *
 * @param[in] p         parameter for the registered function
 * @param[in] flags     pre-shifted content of the ISR register, the bits
 *                      are aligned to bit zero
 */
typedef void (*stm32_dmaisr_t)(void *p, uint32_t flags);

/*===========================================================================*/
/* Driver macros.                                                            */
/*===========================================================================*/

/**
 * @name    Macro Functions
 * @{
 */
/**
 * @brief   Associates a peripheral data register to a DMA stream.
 * @note    This function can be invoked in both ISR or thread context.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 * @param[in] addr      value to be written in the CPAR register
 *
 * @special
 */
#define dmaStreamSetPeripheral(dmastp, addr) {                              \
  (dmastp)->channel->CPAR  = (uint32_t)(addr);                              \
}

/**
 * @brief   Associates a memory destination to a DMA stream.
 * @note    This function can be invoked in both ISR or thread context.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 * @param[in] addr      value to be written in the CMAR register
 *
 * @special
 */
#define dmaStreamSetMemory0(dmastp, addr) {                                 \
  (dmastp)->channel->CMAR  = (uint32_t)(addr);                              \
}

/**
 * @brief   Sets the number of transfers to be performed.
 * @note    This function can be invoked in both ISR or thread context.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 * @param[in] size      value to be written in the CNDTR register
 *
 * @special
 */
#define dmaStreamSetTransactionSize(dmastp, size) {                         \
  (dmastp)->channel->CNDTR  = (uint32_t)(size);                             \
}

/**
 * @brief   Returns the number of transfers to be performed.
 * @note    This function can be invoked in both ISR or thread context.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 * @return              The number of transfers to be performed.
 *
 * @special
 */
#define dmaStreamGetTransactionSize(dmastp) ((size_t)((dmastp)->channel->CNDTR))

/**
 * @brief   Programs the stream mode settings.
 * @note    This function can be invoked in both ISR or thread context.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 * @param[in] mode      value to be written in the CCR register
 *
 * @special
 */
#define dmaStreamSetMode(dmastp, mode) {                                    \
  (dmastp)->channel->CCR  = (uint32_t)(mode);                               \
}

/**
 * @brief   DMA stream enable.
 * @note    This function can be invoked in both ISR or thread context.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 *
 * @special
 */
#define dmaStreamEnable(dmastp) {                                           \
  (dmastp)->channel->CCR |= STM32_DMA_CR_EN;                                \
}

/**
 * @brief   DMA stream disable.
 * @details The function disables the specified stream and then clears any
 *          pending interrupt.
 * @note    This function can be invoked in both ISR or thread context.
 * @note    Interrupts enabling flags are set to zero after this call, see
 *          bug 3607518.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 *
 * @special
 */
#define dmaStreamDisable(dmastp) {                                          \
  (dmastp)->channel->CCR &= ~(STM32_DMA_CR_TCIE | STM32_DMA_CR_HTIE |       \
                              STM32_DMA_CR_TEIE | STM32_DMA_CR_EN);         \
  dmaStreamClearInterrupt(dmastp);                                          \
}

/**
 * @brief   DMA stream interrupt sources clear.
 * @note    This function can be invoked in both ISR or thread context.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 *
 * @special
 */
#define dmaStreamClearInterrupt(dmastp) {                                   \
  *(dmastp)->ifcr = STM32_DMA_ISR_MASK << (dmastp)->ishift;                 \
}

/**
 * @brief   Starts a memory to memory operation using the specified stream.
 * @note    The default transfer data mode is "byte to byte" but it can be
 *          changed by specifying extra options in the @p mode parameter.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 * @param[in] mode      value to be written in the CCR register, this value
 *                      is implicitly ORed with:
 *                      - @p STM32_DMA_CR_MINC
 *                      - @p STM32_DMA_CR_PINC
 *                      - @p STM32_DMA_CR_DIR_M2M
 *                      - @p STM32_DMA_CR_EN
 *                      .
 * @param[in] src       source address
 * @param[in] dst       destination address
 * @param[in] n         number of data units to copy
 */
#define dmaStartMemCopy(dmastp, mode, src, dst, n) {                        \
  dmaStreamSetPeripheral(dmastp, src);                                      \
  dmaStreamSetMemory0(dmastp, dst);                                         \
  dmaStreamSetTransactionSize(dmastp, n);                                   \
  dmaStreamSetMode(dmastp, (mode) |                                         \
                           STM32_DMA_CR_MINC | STM32_DMA_CR_PINC |          \
                           STM32_DMA_CR_DIR_M2M | STM32_DMA_CR_EN);         \
}

/**
 * @brief   Polled wait for DMA transfer end.
 * @pre     The stream must have been allocated using @p dmaStreamAllocate().
 * @post    After use the stream can be released using @p dmaStreamRelease().
 *
 * @param[in] dmastp    pointer to a stm32_dma_stream_t structure
 */
#define dmaWaitCompletion(dmastp) {                                         \
  while ((dmastp)->channel->CNDTR > 0)                                      \
    ;                                                                       \
  dmaStreamDisable(dmastp);                                                 \
}
/** @} */

/*===========================================================================*/
/* External declarations.                                                    */
/*===========================================================================*/

#if !defined(__DOXYGEN__)
extern const stm32_dma_stream_t _stm32_dma_streams[STM32_DMA_STREAMS];
#endif

#ifdef __cplusplus
extern "C" {
#endif
  void dmaInit(void);
  bool_t dmaStreamAllocate(const stm32_dma_stream_t *dmastp,
                           uint32_t priority,
                           stm32_dmaisr_t func,
                           void *param);
  void dmaStreamRelease(const stm32_dma_stream_t *dmastp);
#ifdef __cplusplus
}
#endif

#endif /* _STM32_DMA_H_ */

/** @} */