NRF52芯片的多方面详细阐述

一、低功耗特性

NRF52作为低功耗的芯片在市场上广受欢迎。通常情况下，它在待机模式下的功耗仅有1微安。使用BLE时，它的功率比其他芯片低40％，同时还实现了更远的无线距离。

// Set the advertising parameters
NRF_BLE_ADV_DEF(m_advertising);    
static uint8_t m_adv_handle = BLE_GAP_ADV_SET_HANDLE_NOT_SET;
static ble_gap_adv_properties_t m_adv_properties = {
    .type = BLE_GAP_ADV_TYPE_CONNECTABLE_SCANNABLE_UNDIRECTED,
    .p_peer_addr = NULL,
    .fp = BLE_GAP_ADV_FP_ANY,
    .interval = APP_ADV_INTERVAL,
    .duration = 0,
    .primary_phy = BLE_GAP_PHY_AUTO,
    .secondary_phy = BLE_GAP_PHY_AUTO,
    .channel_mask = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, //all channels
    .max_skip = 0
};
    
// Start advertising.
void advertising_start() {
    uint32_t err_code;
    if(m_adv_handle == BLE_GAP_ADV_SET_HANDLE_NOT_SET) {
        err_code = sd_ble_gap_adv_set_configure(&m_advertising, &m_adv_properties);
        
        APP_ERROR_CHECK(err_code);
        m_adv_handle = err_code;
    
    }
    
    err_code = sd_ble_gap_adv_start(m_adv_handle, BLE_CONN_CFG_TAG_DEFAULT);
    APP_ERROR_CHECK(err_code);
}

// Stop advertising.
void advertising_stop() {
    uint32_t err_code = sd_ble_gap_adv_stop(m_adv_handle);
    APP_ERROR_CHECK(err_code);
}

二、通用天线

NRF52芯片还配备了内置天线，这意味着您无需连接外部天线即可进行通讯。内置天线还可减小系统集成所需的空间，从而使产品设计更加简单。

#define APP_BLE_CONN_CFG_TAG            1                                  /**< A tag identifying the SoftDevice BLE configuration. */

void nrf52_ble_init(void) {
    uint32_t err_code;

    err_code = nrf_ble_init(&m_ble_init, NULL);
    APP_ERROR_CHECK(err_code);

    ble_advertising_init_t init;
    memset(&init, 0, sizeof(init));
    
    init.advdata.name_type          = BLE_ADVDATA_FULL_NAME;
    init.advdata.include_appearance = false;
    init.advdata.flags              = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;

    init.srdata.uuids_complete.uuid_cnt = 1;
    init.srdata.uuids_complete.p_uuids  = &m_adv_uuid;

    err_code = ble_advertising_init(&m_advertising, &init);    
    APP_ERROR_CHECK(err_code);

    ble_advertising_conn_cfg_tag_set(&m_advertising, APP_BLE_CONN_CFG_TAG);
}

三、安全性

NRF52提供了许多内置安全功能，例如AES加密，SHA（安全哈希算法）和True Random Number Generator（TRNG）。AES加密可以在处理器上进行加密和解密，从而提高处理性能并加强加密。使用SHA可以提供数据的完整性和强大的身份验证，而TRNG则可生成真正随机的数字，可以用于密钥生成和其他安全应用。

#define AES_BLOCK_SIZE 16

// Create a single instance of AES context
typedef struct {
    nrf_crypto_aes_context_t enc_ctx;
    nrf_crypto_aes_context_t dec_ctx;
} security_context_t;

security_context_t m_cxt;

// Initialize the encryption / decryption contexts
void security_init(uint8_t *p_key) {
    nrf_crypto_aes_init(&m_cxt.enc_ctx, &g_nrf_crypto_aes_ecb_128_info, p_key);
    nrf_crypto_aes_init(&m_cxt.dec_ctx, &g_nrf_crypto_aes_ecb_128_info, p_key);
}

// Perform encryption of a single block using AES ECB mode
void security_encrypt(uint8_t *p_in, uint8_t *p_out) {
    uint8_t ctext[AES_BLOCK_SIZE];
    nrf_crypto_aes_ecb_encrypt(&m_cxt.enc_ctx, p_in, ctext);
    memcpy(p_out, ctext, AES_BLOCK_SIZE);
}

// Perform decryption of a single block using AES ECB mode
void security_decrypt(uint8_t *p_in, uint8_t *p_out) {
    uint8_t ptext[AES_BLOCK_SIZE];
    nrf_crypto_aes_ecb_decrypt(&m_cxt.dec_ctx, p_in, ptext);
    memcpy(p_out, ptext, AES_BLOCK_SIZE);
}

四、灵活性

NRF52提供许多可编程的外设，这使得它非常灵活，可以针对不同的应用程序进行编程。例如，它允许使用SPI，I2C和USART接口实现许多不同的传输协议。它还支持多种类型的传感器，并具有低功耗特性，适用于物联网设备。

// Initialize the I2C interface
#define I2C_SCL_PIN           15
#define I2C_SDA_PIN           16
#define I2C_FREQUENCY         NRF_TWIM_FREQ_400K

nrf_drv_twi_config_t twi_config = {
  .scl                = I2C_SCL_PIN,
  .sda                = I2C_SDA_PIN,
  .frequency          = I2C_FREQUENCY,
  .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
  .clear_bus_init     = false
};

void i2c_initialize() {
  ret_code_t err_code;

  nrf_drv_twi_init(&m_twi, &twi_config, NULL, NULL);
  nrf_drv_twi_enable(&m_twi);
}

// Read data from a sensor using I2C
uint32_t i2c_read(uint8_t slave_address, uint8_t *p_data, uint32_t data_size) {
  uint32_t err_code;

  err_code = nrf_drv_twi_tx(&m_twi, slave_address, NULL, 0, true);
  APP_ERROR_CHECK(err_code);

  err_code = nrf_drv_twi_rx(&m_twi, slave_address, p_data, data_size);
  APP_ERROR_CHECK(err_code);

  return data_size;
}

// Write data to a sensor using I2C
uint32_t i2c_write(uint8_t slave_address, uint8_t *p_data, uint32_t data_size) {
  uint32_t err_code;

  err_code = nrf_drv_twi_tx(&m_twi, slave_address, p_data, data_size, false);
  APP_ERROR_CHECK(err_code);

  return data_size;
}

五、小结

综上所述，NRF52作为一款低功耗蓝牙SoC具有强大的灵活性和内置安全功能，提供多个可编程外设，使得它成为物联网和其他低功耗应用程序的理想选择。同时，它还配备了内置通用天线，使用起来更加方便。