spi 接收一个字节

	uint8_t cmd2[1] = {0x00};
	char sendbuf2[1];
	char recvbuf2[1];
	memcpy(sendbuf2, cmd2, 1);
	/*
   spi_transaction_t SPITransaction2;
   memset(&SPITransaction2, 0, sizeof(spi_transaction_t));
   SPITransaction2.length = 1 * 8;
   SPITransaction2.tx_buffer = sendbuf2;
   SPITransaction2.rx_buffer = recvbuf2;
   ret = spi_device_transmit(dev._SPIHandle, &SPITransaction2);
   */

	spi_transaction_t recv2;
	memset(&recv2, 0, sizeof(recv2));
	recv2.length = 1 * 8;
	recv2.rxlength = 1 * 8;
	recv2.rx_buffer = recvbuf2;
	ret = spi_device_polling_transmit(dev._SPIHandle, &recv2);

	assert(ret == ESP_OK);
	if (_DEBUG_)
		ESP_LOGI(TAG, "W25Q64_readStatusReg2=%x", recvbuf2[0]);