[introduction]Great majority is based on small controllerThe design uses I2C or SPI, or both hold concurrently with, will realize controller between and the communication between controller and periphery chip. When chip sends specific I2C or SPI data is wrapped, can see embedded the operation of systematic interior is crucial to removing trouble. Make the chip that manages opposite slower parameter more, wait like management of interface of controller of temperature sensor, electric machinery, man-machine or power source, regard as other as the system part as the main measure of communication these bus line. Chip of other high speed, if correspondIntegrated circuit, clock and modulus converter, also undertake configuration through these bus line normally. For example, when power source starts back row to examine cooling fan issue, examine send fan controllerIntegrated circuitSPI jussive sequential and structure, and the drive signal of fan and power source, may help somewhat.

Great majority is based on the design of small controller to use I2C or SPI, or both hold concurrently with, will realize controller between and the communication between controller and periphery chip. When chip sends specific I2C or SPI data is wrapped, can see embedded the operation of systematic interior is crucial to removing trouble. Make the chip that manages opposite slower parameter more, wait like management of interface of controller of temperature sensor, electric machinery, man-machine or power source, regard as other as the system part as the main measure of communication these bus line. Chip of other high speed, be like communication integrated circuit, clock and modulus converter, also undertake configuration through these bus line normally. For example, when power source starts back row to examine cooling fan issue, examine the SPI jussive sequential that sends fan controller integrated circuit and structure, and the drive signal of fan and power source, may help somewhat.

I2C and definition of SPI bus line are specific and relatively dovish, but get possibly still the influence of the delicate difference on problem of layout of noise, board class, restoration and implementation. These problems may bring about bus line mistake and lock to decide sometimes. The oscillograph that provides decipher function can show the state of bus line data and bus line signal at the same time.

I2C

I2C, or ” Inter-IntegratedCircuit ” (the communication between integrated circuit) , it is at first took the place of 1980 first by flying benefit riverside (Philips) of development, aim to supply the means join controller of a kind of low cost and periphery chip. Since then, it has developed become embedded the global standard of the communication between the equipment in the system. This kind of simple crewel design is applied extensively in all sorts of chip, if input / output imitate / digital converter, number / sensor of imitate converter, temperature, small controller and microprocessor, include the product of manufacturer of numerous and banner chip, wait like ADI, Atmel, Infineon, Cypress, Intel, Maxim, NXP, SiliconLabs, ST, TI.

The physical crewel interface of I2C by line of two-way and serial clock (SCL) with data line (SDA) composition. On I2C support bus line many advocate equipment and from equipment, but there can be only inside either time advocate equipment is in mobile condition. Any I2C equipment can receive bus line to go up repeatedly, allow any advocate equipment and exchange information from equipment. Every equipment undertakes discriminating through only address. Equipment can serve as transmitter or receiver according to its function. Support rate of 3 kinds of bit: 100kb/s (standard mode) , 400kb/s (fast mode) with 3.4Mb/s (high speed mode) . The largest amount of equipment is decided by 400pF of the largest electric capacity, it is 20-30 about equipment.

Two kinds of methods can undertake to I2C address in group in order to undertake decipher: One kind is 7 add on one to read write (R/W) plan, another kind is 8 (a byte) , among them R/W the one part that serves as an address. 7 addresses plan is firmware and the designation that software designs an engineer to abide by I2C standard. But a lot of other engineers use 8 addresses program. Tektronix oscillograph is OK decipher the data in these two kinds of plan.

Install decipher of I2C bus line

On Tektronix oscillograph, press the bus line button on next face plate, can define the signal that inputs oscillograph to serve as a bus line. Have clock and data through defining what passageway simply to go up, and use at deciding logic is mixed the digital threshold value of 0, you can make oscillograph understanding crosses the agreement that bus line transmits.

Unscramble I2C bus line

The weaveform related time and bus line decipher show is to a lot of hardware engineers one is familiar with and useful format. The bus line weaveform after decipher showed the element of an I2C message.

To firmware engineer, result form (ResultsTable) the format may be more useful. This kind of bus line activity that brings time stand sth on end shows OK and relaxed ground and software list undertake comparative, and allow relaxed computation implement rate.

As a result the watch still provided the link that returns weaveform to show. You can show in form midpoint attacks group, oscillograph can magnify automatically corresponding bus line signal, the bus line that shows result decipher in the below half part of screen is undee.

Spark on I2C bus line

In be based on the system of one or more serial bus line to debug, a crucial ability of oscillograph is can be kept apart and capture the bus line of specific event sparks. Spark when bus line after be being installed correctly, oscillograph will capture all input signal, and a designation bus line incident will is in by fixed position spark dot. This example was revealed spark on address 0x50 and data 0x00.

In the search on I2C bus line

On Tektronix oscillograph, you can use the Wave Inspector of automation to search a function to find all according with to search bus line incident of the condition, determine the number that they produce. The setting is similar to bus line to spark setting, the bus line event that permits all designation to oscillograph is found and label. In this example, automatic search is searching data to be worth 0x16. This data value appears only in gotten weaveform, serial number uses pink bracket icon to show according to the position of the bag.

SPI

Bus line of serial peripheral interface (SPI) it is its in acting 1980 end by Motolora at first development of 68000 series small controller. As a result of the simple sex of this bus line and welcome degree, come for years a lot of other manufacturer also used this one level. It is applied extensively at now embedded in all sorts of commonly used component in systematic design. SPI basically reachs his with Yu Wei controller between direct peripheral equipment. It is very common in mobile phone and other and mobile equipment, the data that is used between CPU, clavier, indication screen and memory chip corresponds.

Working principle

SPI bus line is advocate / from 4 lines serial communication bus line. These 4 signal are clock (SCLK) , advocate output / from the input (MOSI) , advocate input / from output (MISO) and from the choice (SS) . Every time when two equipment correspond, one is called ” advocate equipment ” , another is called ” from equipment ” . Advocate equipment drive is serial clock. Send and be being received of data undertake at the same time, make its make agreement of a full duplex operation.

Have only address to differ with every equipment on bus line, SPI uses SS line to appoint data is transmit which equipment or come from which equipment. Accordingly, every unique equipment on bus line needs from advocate the SS signal that equipment obtains him. If have 3 from equipment, have 3 SS signal from advocate equipment goes to every from equipment.

SPI also can use the means wiring from equipment cascade, every from equipment ordinal executive operation, remand result hair next advocate equipment (the integrality that this can use method of data of test and verify) .

Below certain circumstance, if arrive from equipment advocate the communication of equipment is not indispensible, MISO signal may be omited completely. Below other condition, have only advocate equipment mixes from equipment, SS signal by ground connection. This is called normally 2 lines SPI.

When producing SPI data to transmit, a 8 digit move on MOSI according to the word piece, go up in MISO at the same time immigrant another 8 data word. This can be regarded as a 16 circular shift register. Should transmit when happening, this 16 shift register is mobile 8 positions, because this exchanged 8 data between equipment of principal and subordinate. A pair of register, clock polarity (CPOL) with clock phasic (CPHA) , decided data is on which clock edge by drive. Every register has two likely state, this allows 4 kinds of possible combination, all these combine each other incompatible. Accordingly, advocate / from equipment same to must be being used parameter value has communication. If used different configuration many from equipment, advocate oneself must be configured afresh when equipment needs to correspond from equipment with what differ every time.

Install decipher of SPI bus line

In this example, the imitate channel that SPI signal carries oscillograph to go up (passageway 1, passageway 2 with the passageway 3) the passive probe that go up is captured. Digital passageway also can be used at bus line decipher. Use bus line configures menu, you can join through appointing clock, data and the passageway from selection signal, threshold value, polarity and word bulk will define SPI bus line.

Unscramble SPI bus line

It is through will showing mode is installed ” bus line and weaveform ” , every number that inputs signal explains OK and fast test and verify (imitate signal and correspondingThreshold value voltagequite) . These digital signal (green expresses tall n, low n of blue colour specification) undertake explanatory according to SPI agreement next. When be installed correctly, oscillograph can show decipher result.

Through total to SPI on-line communication incident undertakes decipher, can identify number easily to begin and end according to what transmit, and transmission specific data content. This identifies potential communication problem to debugging integrality of data of SPI communication, test and verify to reach crucial.

Consider the system of give typical examples of framework of SPI of an use cascade. This subsystem controls a voltage to control an oscillator (VCO) , the others that is a system offers radio frequency clock. VCO is passed advocate CPU writes 6 24 words come initialization. Signal satisfies the electric standard of SPI it seems that, but the frequency with correct without generation VCO.

As a result watch view can use the initialization that checks VCO. Oscillograph can be installed to be in SPI turns into from selection signal spark when mobile condition. When systematic electrify, oscillograph will capture and display initialization array.

Spark on SPI bus line

In above example, we used a simple SS activity to spark. The complete SPI in Tektronix oscillograph sparks ability includes the following type:

These trigger allow you to keep apart and capture the discharge of specific bus line that you are interested in, and the content that decipher function makes you can see every message that has transmitted bus line instantly.

In the search on SPI bus line

To find the incident of all bus line that accords with specific search requirement, the Wave Inspector that can use automation searchs a function. The setting is similar to bus line to spark setting, will be found and label the bus line incident that all designation. In this example, automatic search is searching 24 data to be worth 0x00002X. This data value appeared 23 times in gotten weaveform. Before the navigation arrowhead pushbutton of face plate can be relaxed between the incident of mark navigation. The pink bracket icon near indication bottom showed the place that a when appoint serial data includes.

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