gecko.h

 
#pragma once
 
#include "em_gpio.h"
#include "em_ldma.h"
#include "em_timer.h"
#include "em_usart.h"
 
#include "sl_sleeptimer.h"
 
#include <joybus/bus.h>

#define JOYBUS_GECKO(bus) ((struct joybus_gecko *)(bus))
 
// Number of chips per bit for the line coding
#define CHIPS_PER_BIT           4
 
// Edges per byte for pulse timing decoding
#define EDGES_PER_BYTE          16
 
// Private implementation details - do not access directly
struct joybus_gecko_data {
  // Bus state
  uint8_t state;
 
  // GPIO configuration
  GPIO_Port_TypeDef gpio_port;
  uint8_t gpio_pin;
 
  // Peripherals
  TIMER_TypeDef *rx_timer;
  USART_TypeDef *tx_usart;
 
  // RX/TX state
  uint8_t *read_buf;
  uint8_t read_len;
  uint8_t read_count;
  uint8_t *write_buf;
  uint8_t write_len;
  bool rx_trailing_bit;
  sl_sleeptimer_timer_handle_t rx_timeout_timer;
 
  // Transfer state
  joybus_transfer_cb done_callback;
  void *done_user_data;
 
  // RX timings
  uint16_t pulse_period_half;
  uint16_t bus_idle_period;
 
  // RX ping-pong LDMA configuration
  unsigned int rx_dma_channel;
  uint16_t rx_edge_timings[2][EDGES_PER_BYTE + 2];
  LDMA_TransferCfg_t rx_config;
  LDMA_Descriptor_t rx_descriptors[2];
  uint8_t rx_current_buffer;
 
  // TX ping-pong LDMA configuration
  unsigned int tx_dma_channel;
  uint8_t tx_encoded_bytes[2][CHIPS_PER_BIT];
  LDMA_TransferCfg_t tx_config;
  LDMA_Descriptor_t tx_descriptors[3];
  uint8_t tx_initial_buffer;
  uint8_t tx_current_buffer;
  uint8_t tx_buffered_bytes;
};

struct joybus_gecko {
  struct joybus base;
  struct joybus_gecko_data data;
};

struct joybus_gecko_config {
  GPIO_Port_TypeDef gpio_port;

  uint8_t gpio_pin;

  TIMER_TypeDef *rx_timer;

  USART_TypeDef *tx_usart;

  uint32_t freq;
};

static inline struct joybus_gecko_config joybus_gecko_config_default(GPIO_Port_TypeDef port, uint8_t pin)
{
  return (struct joybus_gecko_config){
    .gpio_port = port,
    .gpio_pin  = pin,
    .rx_timer  = TIMER0,
    .tx_usart  = USART0,
    .freq      = JOYBUS_FREQ_NOMINAL,
  };
}

int joybus_gecko_init(struct joybus_gecko *gecko_bus, struct joybus_gecko_config config);