DS1621 IIC interface under Linux drives designing

Description: The IIC bus line is a type of communication protocol that facilitates the transmission of data between devices. It is characterized by its simplicity in construction and wiring, making it suitable for various high-performance applications. The operating system, particularly Linux, is widely used for embedded systems, enabling easy access to source code for developers. In this context, the IIC bus line allows for collaboration between an ARM processor and peripheral modules, demonstrating extensive applicability. The IIC, or I2C, consists of two signal lines: a two-way data line (SDA) and a clock line (SCL). This bus supports half-duplex synchronous data transmission due to its straightforward structure. The IIC bus operates with one master device at a time, which controls the communication process by sending clock signals and addressing slave devices. Each device on the IIC bus has a unique address, facilitating communication initiated by the master. The transmission starts when the SCL line is high (1) and the SDA line transitions from high (1) to low (0), indicating the beginning of data transmission. The transmission stops when SCL is high (1) and SDA transitions from low (0) to high (1). During the high state of the SCL line, the data on the SDA line must remain stable, and changes can only occur when SCL is low. Each byte transmitted on the SDA line consists of 8 bits, with an acknowledgment (ACK) signal following each byte. The microcontroller used in this design is the S3C2440, a 16/32-bit RISC embedded microprocessor based on the ARM920T core, designed for handheld devices with a focus on cost-effectiveness and low power consumption. It integrates an IIC bus control unit, facilitating communication with IIC-compatible peripheral devices. The DS1621, a digital temperature sensor and thermostat controller produced by DALLAS Company, is compatible with the IIC bus and can control up to eight DS1621 devices. It operates at a voltage range of 2.7 to 5.5 V, making it ideal for low-power applications. The DS1621 can function independently as a thermostat or communicate temperature measurements to the ARM processor through its two-wire interface. Configuration and adjustments are made via registers, and it does not require additional components for temperature measurement. The DS1621 provides a 9-bit digital output, with a measurement range of -55 to 125°C and a precision of ±0.5°C, with a typical response time of 1 second. In this circuit design, the S3C2440 microcontroller acts as the master device controlling the IIC bus, while two DS1621 sensors serve as slave devices. The SDA and SCL lines of the S3C2440 are directly connected to the DS1621 devices, with chip selection signals provided through specific pins to determine the active slave address. Since IIC slaves typically utilize MOS technology, pull-up resistors are employed on the bus lines to ensure proper signal integrity during operation. The DS1621 is configured to function as a temperature sensor through the IIC bus interface.IC bus line explains conduct and transmits the bus line as one kind, it uses and is wired little, simple in construction, it is the extensive high-performance bus line way of a application. The operating system that and Linux cuts out publicly and easily as a source code, is very suitable for the application of the embedded system.

The embedded apparatus under Linux operating system is driven, through IIC bus line, realize the collaborative work among ARM and peripheral module, there is extensive application. IIC I2C made up of two sticks of signal line: A two-way transmissive data link SDA; Another one is a clock line SCL.

IIC bus line can realize half duplex synchronous data transmission through the simple structure. Adopt one main fact more than IIC bus line from operating mechanism, at one time can only have one of apparatuses as master, by main device control, main the intersection of device control and machine format the intersection of conveyance and initiating signal, send out clock signal, the intersection of slave and address signal, intelligence signal total collinear operation, the receive data side sends out the answer back signal while conveying finishing, the apparatus on each IIC bus has an only address, and the master carries on communication. IIC bus line sequence is shown as in Fig. 1, while IIC bus line uses, the start of transmission and condition stopped are as follows: As SCL sustains  1 ³ And SDA is from  1  Turn into  0  Show hour that will begin the transmission data; And sustain SCL  1 ³ And SDA is from  0  Turn into  1  Show that stops the transmission data.

Among them the data on the SDA line are in the clock line SCL  1 ³ It must be stable during this time, only when the clock signal on the SCL line is for being low the state on the line of the data could change. Each byte on the SDA line must be 8, the transmissive number of bytes is not limited each time, sending the one byte each time all has acknowledgement location of one ACK.

MCU adopts S3C2440 chip of one company, S3C2440A is an 16/ 32 RISC embedded microprocessors based on ARM920T kernel of one company, mainly face the application of handheld device and high cost performance, low power consumption, integrate 1 the intersection of IIC and bus control unit, can convenient the communication with IIC interface peripheral hardware. DS1621 is a kind of powerful digital temperature sensor and thermostatic controller that DALLAS Company produces.

The interface is compatible with IIC bus line, a slice of control device can control up to 8 slices of DS1621s to control, working voltage is 2. 7- 5. 5 V, are suitable for the application system of low power consumption. DS1621 can be regarded as the thermostatic controller and used singly, can also finish measurement and calculation of the temperature under the control of ARM through 2 line interfaces.

Can set up and adjust through the register. DS1621 does not need peripheral component namely temperature of measurable quantity, the result is with 9 digital quantity two bytes Provide, the measurement limit is 55 155, the precision is 0. 5 : Typical change-over time is 1 s. Design adopting S3C2440 as the master in the circuit, control it from the device on IIC bus line, clock signal and various intelligence signals from the main device control IIC bus line.

Adopt 2 slices of DS16 21 as the slave on IIC bus line, because DS1621 possesses IIC bus interface, can be connected to SDA and SCL foot of S3C2440 directly, pass A2, A1, the intersection of A0 and foot in DS1621 5, 6, 7 feet Make up, input different the intersection of chip selection and signal, can confirm the intersection of slave and address that work under the intersection of IIC and bus line it. Because IIC slaves are generally all mos technologies, the bus line is pulled upward the resistance. While working, set up DS1621 as the temperature sensor function through IIC b