Keyboard: Helix serial improvements (#3608)

* add change_reciver2sender()/change_sender2reciver()

This is a change to improve readability.

* txled, rxled off in matrix_init()

* add serial_send_packet() / serial_recive_packet()

This is a change to reduce object size.

* add serial_low() at ISR() top

* add __attribute__((always_inline)) to some functions

* modify serial_send_packet()/serial_recive_packet()

A little, object size reduction.
A little, speedup.

* add debug code to helix/serial.c

* Adjust sampling timing of serial signal being received

* add split_scomm.c/split_scomm.h and change serial.c/serial.h

serial.c was divided into 2 layers, split_scom.c and serial.c.
The upper layer split_scomm.c is called from matrix.c.
The lower layer serial.c accesses the hardware.

* add split_scomm.c/split_scomm.h into helix/rev1

* reduce object size helix/rev2/matrix.c

* remove checksum check, add parity check

* force occur parity error for test

* parity test ok. remove test code

* change some comment & add skip code when buffer_size == 0

* serial.c: multiple types of transaction support

Add 4 bits transaction-type field at packet top.
Select Transaction Descriptor Table entry by transaction-type.

* helix serial master-slave transaction optimize

Using multi-type transaction feature of serial.c, communication contents between master slaves were optimized.

* add debug code for retry

* add comment into each config.h

* fix ISR status drop

* add a debug macro 'debug_retry_chg()'

* reduce led_test size

* remove debug code from helix/serial.c and etc.

* helix:five_rows change TAPPING_TERM value 140

* Improved compatibility with let's split of serial.c. Finish helix/serial.c improvement.

- The difference with the original let's split's serial.c
  - It's high-speed about 4 times.
  - Stable bi-directional data transfer. (Helix need master to slave transfer)
  - serial.h was divided 2 files, serial_config.h and sereial.h
  - With multiple types of transaction support, communication contents can be optimized. (NEW flexible API)

- USE OLD Simple APIs (compatible with let's split serial.c)
  - files :
    - serial_config.h -- hardware configuration (need include by config.h)
    - serial.c/serial.h -- serial communication

- USE NEW flexible APIs. (Support multi-type transaction function.)
  serial.c was divided into 2 layers, split_scom.c and serial.c.
  The upper layer split_scomm.c is called from matrix.c.
  The lower layer serial.c accesses the hardware.
  - files
    - split_scomm.c -- communication buffer is defined in here. call by matrix.c.
    - split_scomm.h -- buffer size is defined in here. include by matrix.c, split_util.c
    - serial_config.h -- hardware configuration (need include by config.h)
      To use the NEW API, specify #define SERIAL_USE_MULTI_TRANSACTION
    - serial.c/serial.h -- serial communication lower layer

- NEW APIs for serial.c / serial.h (The lower layer)
  // Soft Serial Transaction Descriptor
  typedef struct _SSTD_t  {
      uint8_t *status;
      uint8_t initiator2target_buffer_size;
      uint8_t *initiator2target_buffer;
      uint8_t target2initiator_buffer_size;
      uint8_t *target2initiator_buffer;
  } SSTD_t;

  // initiator is transaction start side
  void soft_serial_initiator_init(SSTD_t *sstd_table);
  // target is interrupt accept side
  void soft_serial_target_init(SSTD_t *sstd_table);
  int soft_serial_transaction(int sstd_index);
  int soft_serial_get_and_clean_target_status(int sstd_index);

- NEW APIs for split_scomm.c / split_scomm.h (The upper layer)
   move from old serial.c the following buffer and functions
     serial_slave_buffer[]
     serial_master_buffer[]
     void serial_master_init(void)
     void serial_slave_init(void)
     int serial_update_buffers(void)
   define SERIAL_xxxxx_BUFFER_LENGTH move from serial_config.h to split_scomm.h

3 files changed, 4 insertions, 4 deletions

diff --git a/keyboards/helix/rev1/keymaps/OLED_sample/serial_config.h b/keyboards/helix/rev1/keymaps/OLED_sample/serial_config.h
index be2e7cb8b..b991b874b 100644
--- a/keyboards/helix/rev1/keymaps/OLED_sample/serial_config.h
+++ b/keyboards/helix/rev1/keymaps/OLED_sample/serial_config.h
@@ -9,7 +9,7 @@
 #define SERIAL_PIN_INTERRUPT INT2_vect
 
 #define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
-#define SERIAL_MASTER_BUFFER_LENGTH 1
+#define SERIAL_MASTER_BUFFER_LENGTH 0
 
 //// #error rev1/keymaps/OLED_sample serial config
 
diff --git a/keyboards/helix/rev1/rules.mk b/keyboards/helix/rev1/rules.mk
index daba80eae..13834f5da 100644
--- a/keyboards/helix/rev1/rules.mk
+++ b/keyboards/helix/rev1/rules.mk
@@ -1,4 +1,4 @@
-SRC += rev1/matrix.c \
-	   rev1/split_util.c
+SRC += rev1/matrix.c
+SRC += rev1/split_util.c
 
 BACKLIGHT_ENABLE = no
diff --git a/keyboards/helix/rev1/serial_config.h b/keyboards/helix/rev1/serial_config.h
index 2b668a6af..51c6aa375 100644
--- a/keyboards/helix/rev1/serial_config.h
+++ b/keyboards/helix/rev1/serial_config.h
@@ -9,7 +9,7 @@
 #define SERIAL_PIN_INTERRUPT INT0_vect
 
 #define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
-#define SERIAL_MASTER_BUFFER_LENGTH 1
+#define SERIAL_MASTER_BUFFER_LENGTH 0
 
 /// #error rev1 serial config