Evolution of ROHM's wireless LAN module technology

　　The ROHM Group has a variety of wireless communication technologies, including Bluetooth, ZigBee, and wireless LAN, as well as specific low-power wireless technologies for the 920MHz frequency band opened in Japan in July 2012.

　　Through the integration of technology with LAPIS Semiconductor, a group company, ROHM has product advantages from wireless communication ICs to modules, and in line with customer needs, provides customers with communication ICs and modules that fully utilize the characteristics of radio waves in various communication standards. In particular, wireless communication ICs use LAPIS Semiconductor's proud low-power RF-CMOS technology and high-performance MODEM technology to achieve the industry's highest level of low power consumption and wireless performance, which is also a major feature of this type of product.

　　Background

　　Nowadays, with the growing demand for wireless communications in various fields around the world, the requirements for high-standard technology and high performance have also risen. Especially when expanding to industrial control, automotive and other fields, due to the harsh environment, many issues need to be solved to achieve popularization. In this regard, Rohm relies on its own advantages of a "one-stop" production system starting from IC to meet the various needs of the market, and combines innovative technologies to present a more complete and higher-standard wireless LAN module, making a new breakthrough in module technology.

　　ROHM launches new wireless LAN modules "BP3580/BP3591"

　　This time, Rohm has launched a new wireless LAN module "BP3580/BP3591" that supports the IEEE802.11b/g/n standard (as shown in the right picture). Rohm's wireless LAN module "BP3580/BP3591" has been fully adjusted including the RF part. It not only has basic wireless LAN communication functions, but also has the authentication and encryption Supplicant (client authentication software) and WPS (Wi-Fi Protected Setup, a specification for encryption settings between wireless LAN devices) that are usually built into the host side.

　　In addition, the module has a built-in TCP/IP protocol stack, so that all network processing can be completed by the module. Therefore, even white goods and health equipment that are difficult to configure wireless LAN due to insufficient host resources can easily be equipped with wireless LAN. In addition to the surface mount type "BP3580", the product lineup has added the built-in antenna "BP3591" (for the UART interface with the host) that can be connected via a connector.

　　Figure: Wireless LAN module "BP3580/BP3591"

　　The built-in antenna eliminates the need for high-frequency design, which requires advanced technical know-how, and the product has been certified under Japan's domestic radio law, so it can be used as a wireless device as soon as it is assembled into a supporting device.

　　"BP3580/BP3591" integrates innovative technologies and has unique advantages

　　The biggest feature of the BP3580/BP3591 is that it has a built-in baseband IC (BU1805GU) produced by ROHM. By using a self-produced baseband IC, more complete development support and long-term stable supply can be achieved.

　　[Figure 1] Features of BP3580/BP3591

　　As shown in Figure 1, the baseband IC and module, as well as the software and hardware of the "BP3580/BP3591" products are all developed by ROHM, so there is absolutely no black box inside, which makes development support more complete. Similarly, the "one-stop" production system starting from the IC will not cause production to stop due to external factors, so long-term stable supply is also a strength of this product. In addition, sufficient connection tests have been implemented to achieve very high-quality connection stability. Regarding the certification of the radio law, the "BP3591 (antenna built-in type)" module has obtained the radio law certification of Japan and the United States (FCC). The "BP3580 (surface mount type)" is also ready to easily obtain the Japanese radio law certification. It can operate with a single 3.3V power supply and covers the operating temperature range of -40℃~+85℃.

　　Table 1 shows the specifications of "BP3580/BP3591". The SDIO general-purpose type and USB general-purpose type are designed for systems where the TCP/IP protocol stack is installed on the host microcontroller side. The TCP/IP protocol stack built-in type is designed for systems where RS-232C interface devices are connected to wireless LAN or systems where the TCP/IP protocol stack is not installed on the host microcontroller side. ROHM has prepared firmware for the SDIO general-purpose type, USB general-purpose type, and TCP/IP protocol stack built-in type for customers. The hardware of "BP3580/BP3591" is common, and the model is selected by changing the downloaded firmware.

　　[Table 1] "BP3580/BP3591" Specifications Overview
Figure 2 is a block diagram of "BP3580/BP3591". "BP3580" is a surface mount type, and "BP3591" is a built-in antenna type. In addition, as mentioned above, when using these modules, it is necessary to download the firmware from the HOST CPU or flash memory each time it is started. When there is no storage area for storing firmware in the HOST CPU, the module has a flash memory startup function. As long as the flash memory is prepared externally, the firmware can be automatically read and run when the power is turned on.

　　[Figure 2] Block diagram of “BP3580/BP3591”

　　ROHM's firmware lineup is shown in Table 2, and customers can freely select firmware according to their application. ROHM has already announced STA (station) type ① and AP (Access Point) type ③ of firmware (USB and SDIO interfaces) that it positions as "standard", and STA (station) type ② and AP (Access Point) type ④ of TCP/IP built-in firmware (UART interface), and is also developing standard firmware ⑤ that supports Wi-Fi Direct and TCP/IP built-in firmware ⑥.

　　[Table 2] Firmware lineup for "BP3580/BP3591"

　　Next, the firmware is explained using the software protocol stack diagram in Figure 3. The left side shows the software protocol stack diagram when using standard firmware ① and ③, and the right side shows the software protocol stack diagram when using TCP/IP built-in firmware ② and ④. The upper part is the HOST side software (software that needs to be prepared by the customer), and the lower part is the software stored on the wireless module side.

　　One of the features of the standard firmware on the left is that the software (Supplicant) for processing wireless LAN authentication and security such as WPS, WPA/WPA2, etc., which is enclosed by a dotted circle, is stored on the wireless module side.

　　Therefore, customers do not need to prepare these. In addition, the HOST side requires a Wireless LAN Device Driver module, which is a very large part of the development burden for customers, but ROHM has prepared a developed Device Driver and can provide customers with OS Linux version driver reference source code free of charge.

　　The TCP/IP built-in firmware on the right is a firmware that stores the TCP/IP protocol stack on the wireless module side based on the standard firmware's Supplicant. In addition, ROHM's unique WID command is available, and the module can be commanded and controlled from the host side using the WID command. In other words, the TCP/IP protocol stack is stored on the module side and controlled by commands, making it possible to install a wireless LAN "without a driver".

　　Since it does not require a driver, the customer's development period can be greatly shortened compared to conventional wireless LANs. In addition, the HOST CPU specification requirements are also low, and only an 8-bit CPU is required for control.

　　In addition, the STA firmware has the "DHCP Client" and "WPS Enrollee" functions installed, and the AP firmware has the "DHCP Server" and "WPS Registrar" functions installed.

　　[Figure 3] “BP3580/BP3591” software protocol stack composition

　　The TCP/IP protocol stack built-in type has two modes. The first is the "terminal mode" in which wireless connection can be easily achieved by inserting "BP3580/BP3591" between terminals connected by RS-232C; the second is the "communication mode" in which more complex work can be achieved by simple socket programming on the host side.

　　Table 3 shows the specifications of the TCP/IP protocol stack. For example, by installing the SMTP and POP3 protocols on the host microcontroller side using the TCP port, the function of sending and receiving messages can be realized.

　　In the future: Rohm will actively promote the development of wireless LAN modules

　　In the development of wireless LAN modules, ROHM has adopted the development concepts of "easy to use (even if you have no experience)" and "providing full support". Not only now, but also in the future, ROHM will continue to improve its global support system, make full use of the advantages of its own ICs, and promote the development of new products at any time to present users with a more comprehensive technical experience.