Optical module weapon - EFM8 8-bit MCU with pre-installed I2C bootloader

Silicon Labs (also known as Core Technology) pre-installs a bootloader with I2C , ^UART or USB download functions in its entire series of EFM8 8- bit MCUs for program updates when they leave the factory, and provides source code for users to customize the bootloader . This is undoubtedly a shot of stimulant for the vast number of optical module R&D engineers.

What is Bootloader ?

As the name implies, Bootloader has the functions of Boot system and Loader system update. Its function is similar to that of computer BIOS . It is the first code executed after MCU is powered on. After completing the initialization of CPU and related hardware, it determines whether the system should enter Boot mode or Loader module at this time ^. In Boot mode , MCU will jump to user code to execute user program; in Loader mode, MCU receives data transmitted by I2C , UART or USB , overwrites the user program code area, and updates the program code.

By presetting the Bootloader , users can update and upgrade the program directly on the communication interface without using the debugging interface and tools, which greatly facilitates users to update product programs.

Why does an optical module need a built-in I2C Bootloader ?

For a long time, due to hardware limitations, Bootloader has been limited to 32- bit embedded systems with large performance and storage capacity as a function of booting the operating system. With the increasing demand for volume, function, application and debugging of modern electronic products, the demand for Bootloader has also begun to appear on 8 -bit MCUs , and optical modules are particularly strong in this regard.

The function of the optical module is photoelectric conversion. The transmitting end converts the electrical signal into an optical signal. After being transmitted through the optical fiber, the receiving end converts the optical signal into an electrical signal. The size of the optical module is very small, which is a great challenge for hardware engineers to wire. Many engineers rack their brains to reserve the program download interface. Since the optical module generally uses I2C Slave to receive data, the built-in I2C Bootloader for program update can greatly facilitate the design of hardware engineers and facilitate mass production for customers.

I2C Bootloader Implementation for EFM8 ^​

Silicon Labs ' 8 -bit MCUs are favored by optical module manufacturers due to their small size, low power consumption, few peripheral devices and stable performance. Its C8051F33X , C8051F39X and C8051F85X series of 8 -bit MCUs are widely used in the field of optical modules. This year, Silicon Labs continued to make efforts to launch the low-cost EFM8BB series and high-performance EFM8LB series MCUs for the optical module market , and added Bootloader to the entire EFM8 product line .

The principle of updating the program of the computer through the USB or serial port through the EFM8 is shown in Figure 1 :

Figure 1 : EFM8 USB and serial port download

The download software on the computer first converts the firmware HEX file executed on the lower computer into a binary record file, and then splits the file content into multiple data packets and transmits them to the EFM8 Bootloader in batches. After receiving the data , EFM8 unpacks it and updates the user program area code.

Since the computer does not have an I ² C interface, the I2C download of EFM8 requires the addition of an MCU to perform UART to I ² C protocol conversion, as shown in Figure 2 :

Figure 2 : EFM8 I2C Download ​ ^​ ​

Currently, Silicon Labs provides a complete set of source code for UART to I ² C protocol conversion based on C8051F37X and C8051F39X , and customers can also easily port it to other platforms.

The built-in Bootloader of EFM8 is located on its code security page, ensuring that the Bootloader can still update the program correctly when the Flash page is locked. At the same time, if the customer does not need the Bootloader , the downloader can also be used to erase and release the Flash space.

In summary, Silicon Labs fully considers the needs of optical modules and adds the I2C download function to EFM8 in a timely manner , while continuing to maintain its industry advantages of small size and low power consumption, which will undoubtedly increase product competitiveness and enable it to continue to maintain its leading position in the optical module market share.

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