Tag Archives: wireless communication

Seg 1: WIFI wireless communication module serial debug based on the Arduino shield board

2.1 Problem presentation: how to use serial tools to debug wifi module?

In this part, we will discuss whether a new wifi module works normally. For this purpose, we can from the following two aspects.

  1. From the wifi hardware, we can judge whether a new wifi module normally work from its pilot lamp;
  2. By using the serial tools to debug the wifi module from software. Note that, in this section, the serial software includes mobile and computer (PC) version.

2.2 Hardware and software

For debug whether a new wifi module normally work, we need the following hardware and software, as shown in Table 2-1.

Table 2-1 the required materials


name quatity function note


Wifi module 1 Wireless communication


Arduino shield 1 Wifi connection


USB to RS232 1 Transformation and connetion


5V1A voltage adapter 1 Provide voltage


antenna 1 Transmit wifi signal


PC tools 1


Mobile tools 1

The required materials are shown in Figure 2-1.

Figure 2-1 Hardware of network serial debug

Seg 3: wifi features and frequency band

  1. Features of Wifi
  • Constitution of network is flexible. It can be infrastructure mode, or a self-organizing mode;
  • Mature technology and rich application;
  • Low price devices;
  • Low power, small recover range;
  • Woring at the frequency 2.4GHz, which is the same as IMS (Industrial/Medical/Scientific). Thus, it may be relatively easy to be interfered. Moreover, Microwave ovens, and cordless phone are also working at IMS frequency.
  1. Wireless frequency band

ISM frequency band is reserved for the Industrial/ Scientific / Medical use, which is specialized by FCC. Nowadays, most countries all over the world open this frequency band by following this standard. But the ISM frequency is not unified in these countries. We cannot be allowed to use these frequency bands, i.e., 900MHz, 2.4GHz, 5.7GHz; but the transmitted power must be lower the specialized power (generally lower 1W) and the utilized frequency cannot interfere with other frequencies. At present, most of the wireless products are working at 2.4GHz. And the 802.11 protocol families are shown in Table 1-1.

Table 1-1 Wireless Frequency





Release time

Sept. 1999

Sept. 1999

June. 2003

Jan. 2004





2.4Ghz5Ghz(2.4Ghz or/and 5Ghz







About 100m

About 50m


Several Km

Max rate







Not with 11b/g




Seg 2: Wifi history

  • In 1996, Lucent in America firstly launched to set up Wireless Ethernet Compatibility Alliance (WECA), which aimed at the wireless local area networks (WLAN).
  • In 1999, WECA was renamed as Wi-Fi alliance, which would design an approval standard again. In this case, the alliance presented a series of wireless networks technology 802.11 in wireless communication, such as 802.11b, 802.11a, 802.11g, 802.11n, and so on.
  • Wi-Fi alliance committed itself to generate the 802.11 products and to solve the compatible problems. Note that, 802.11 is not denoted the wireless network. It is just one of the wireless networks.
  • Wireless Local Area Network can be abbreviated as WLAN. By this wireless communication technology, all the computer devices, pda, mobile phone and other many connectable devices, could communicate with each other by the wireless networks. Furthermore, if we use the wireless communication networks, all of the devices can be connected each other with no cable. It is would be much more mobile and flexible. Fortunately, wifi is the kind of wireless networks technology.

    Figure 1-2 wireless communication networks

  • Difference between Wifi, bluetooth, and ZigBee: bluetooth (BLE) is one of the WPAN (Wireless Personal Area Networks) technology, while wifi belongs to WLAN (Wireless Local Area Networks) technology. The two technologies can provide the different wireless networks services. Moreover, there exists an entitative difference for the realization of the two technologies.
  • The effects of WIFI radiation on human body: general speaking, the transmission power is much weaker than that of the mobile phone. For example, the transmitted power is about 60~70mW, while for mobile phone, the power is 200mW or so. What is more, wireless cannot directly touch the people tissue, but mobile phone must. So, the power to body is less than 1mW, and thus can be ignored.

Seg 1: What is wifi

  1. Problem presentation: know Wi-Fi

In the basic part of Arduino, we have known Arduino to some extent. From this part, we will come to learn the knowledge on the combination of Arduino and wireless communication, which can promote us interact with Arduino. In the first chapter, we will simply get at the relevant concepts and basic knowledge about Wi-Fi (which is also written as wifi) to prepare the future work.

  1. What is wifi

WIFI is the abbreviation of Wireless Fidelity, which is a technology working in the vicinity of the frequency 2.4/5GHz. Its velocity is relative high, and the distance is relative long. Moreover, it is compatible with the existing 802.11 DSSS devices. DSSS (Direct Sequence Spread Spectrum) is a wireless sequence transformation way with high security and anti-interference. DSSS can extend the signal spectrum at send end by utilizing the high velocity spread sequence. Naturally, at the receive end, by using the decoding with the same spread spectrum code sequence, the extended signal can restore to the original signal. This is the principle of direct sequence spread spectrum (DSSS). Wifi can be read as [waifai]. The wireless router shown in Figure 1-1 is already used the wireless communication technology, i.e., wifi.

Figure 1-1 Wi-Fi wireless router