Abstraction for S3C2440 bare board programming (without operating system)

          In the embedded field, almost all device controls and various protocol controls are in the same embedded CPU, which is very conducive to abstracting the CPU Core and devices. If the CPU Core and various device controls can be abstracted, people do not need to have a very deep understanding of the CPU when porting the OS or developing drivers, and do not need to understand what a certain bit of a register controls, nor do they need to understand how to initialize a certain control register, etc.

        When using the controller to write a bare board application, the programmer only needs to understand the initialization sequence and content of the controller without understanding the specific details of the initialization to complete the application. Obviously, it can greatly improve work efficiency, and the specific details of the hardware are the most error-prone part of the application, and the use of the controller can greatly reduce the possibility of errors.
        ARM is a more powerful single-chip microcomputer. In the process of learning bare metal programming, it is found that ARM integrates more peripherals than ordinary single-chip microcomputers (general single-chip microcomputers only integrate serial ports and four groups of IO ports), contains more GPIOs, and has more registers. The relevant pins are controlled by setting and enabling registers to control related devices. S3C2440 has an internal hardware controller integrated, and various driver protocols are generated by the hardware controller. We only need to configure the registers of the corresponding hardware controller to generate the corresponding driver timing. High-end ARM learning is mainly based on software programming (i.e., understanding). It has rich resources and rarely needs to expand peripherals. The focus of learning is how to configure registers and how to write applications.

        Just set the corresponding control registers and read and write the corresponding data registers. The key to learning bare board program development is to understand the principles of various interface protocols, so that you can understand the initialization sequence and content of the controller.

        The following is an example of the S3C2440 I2C controller. The following program is based on the interrupt mode. For the explanation of the I2C protocol, you can check my previous blog. The I2C protocol stipulates that after the receiver receives a byte (address or data), it must send an ACK. After the transmitter receives the ACK, it can continue to send data or end data transmission. After the receiver (here we are the S3C2440 I2C controller) receives the ACK, an interrupt will be generated. In the interrupt handler, you can continue to send the program or end the transmission. Understanding the basic principles of the I2C protocol, writing programs is a piece of cake.