CN109217875B

CN109217875B - Manchester coding and decoding method

Info

Publication number: CN109217875B
Application number: CN201811245840.9A
Authority: CN
Inventors: 任正
Original assignee: Nanjing Qinheng Microelectronics Co ltd
Current assignee: Nanjing Qinheng Microelectronics Co ltd
Priority date: 2018-10-24
Filing date: 2018-10-24
Publication date: 2022-08-26
Anticipated expiration: 2038-10-24
Also published as: CN109217875A

Abstract

The invention discloses a Manchester coding and decoding method, S1, the initial frame is read, the initial frame is continuous N1, because the stop bit is 0, the initial frame following immediately is 1, the first bit of the initial frame is 1 jump, namely in N T0 cycles, jump is necessary every 1/2T 0, 2N-1 jump edges exist, whether 2N-1 jump exists is detected in N T0 time, if yes, the initial frame is judged to be correct, at this time, the data is read and recorded; s2, reading the data frame, immediately entering a data frame reading stage after the reading of the initial frame is finished, delaying the time by more than 1/2 x T0 to less than T0, waiting for the jumping edge, wherein the jumping level data is the bit data of the current data frame; and S3, checking whether the data reading is correct. The invention only needs 1 timer, only needs to record jump time, can greatly reduce software overhead, save RAM and ROM.

Description

Manchester coding and decoding method

Technical Field

The invention relates to a Manchester encoding and decoding method, belonging to the technical field of integrated circuits.

Background

RFID is widely adopted in the electronic field, and the decoding of 125KHz RFID code can be realized by a special chip or single chip microcomputer software. The hardware complexity is increased and the production cost is increased by using a special chip, the common singlechip software for decoding Manchester codes needs to start the edge capture of a timer and store the duration time of high and low levels, and the inverted level is judged to be high or low or idle jump according to the duration time of the high and low levels.

Disclosure of Invention

In order to solve the problems, the invention provides a Manchester coding and decoding method, which only needs 1 timer and only needs to record the jump time, thereby greatly reducing the software overhead and saving RAM and ROM.

The technical scheme for solving the problems is as follows: a Manchester encoding and decoding method comprises the following steps:

s1, reading a start frame, wherein the start frame is continuous N1, because the stop bit is 0, the start frame immediately following the stop bit is inevitably 1, the first bit of the start frame is inevitably 1 jump, namely in N T0 periods, jump is inevitably carried out every 1/2T 0, 2N-1 jump edges are provided, whether 2N-1 jump exists is detected in N T0 time, if yes, the start frame is judged to be correct, and data is read and recorded at the moment;

s2, reading the data frame, immediately entering a data frame reading stage after the reading of the initial frame is finished, delaying the time by more than 1/2 x T0 to less than T0, waiting for the jumping edge, wherein the jumping level data is the bit data of the current data frame;

and S3, checking whether the data reading is correct.

Further, the specific step in S1 is to set the effective jump time of the start frame to be 20 × T1-30 × T1, if jump occurs in this interval, add 1 to the effective count of the start frame, otherwise, clear the effective count of the start frame; and if the effective counting value of the initial frame is more than or equal to 2N-2, entering a data frame reading stage.

Further, the specific steps in S2 are that, after the start frame is read, the data frame is directly read, the time is delayed by 4/5 × T0, that is, by 40 × T1, the edge jump is waited, the level data after the jump is recorded, and the data counter is incremented by 1; if the data counter is more than or equal to 55 bits, the reading of the data frame is finished.

Further, row-column parity or redundancy check is employed in S3.

Further, the specific step of performing parity check on the data frame is that the fifth number of each row and the tenth number of each column are respectively subjected to parity check, and if the row and column checks are passed, the RFID tag is indicated to receive correctly.

The invention has the advantages that: by judging the initial frame and reading data, the method saves the edge capturing and timing, only needs 1 timer, only needs to record the jump time, can greatly reduce the software overhead, and saves RAM and ROM.

The present invention is described in further detail below with reference to the attached drawing figures.

Drawings

FIG. 1 is a schematic diagram of determining a start frame;

FIG. 2 is a schematic diagram of data frame determination;

FIG. 3 is a flowchart of start frame determination code;

fig. 4 is a flow chart of a data frame code.

Detailed Description

For the purpose of enhancing the understanding of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, which are only used for explaining the present invention and are not to be construed as limiting the scope of the present invention.

Referring to fig. 1-4, the present invention provides a manchester encoding and decoding method, which comprises

The carrier frequency of the 125KHz RFID signal is 125KHz, the frequency of the modulated signal is 2KHz, and Manchester coding is adopted, and the encoding mode of Manchester coding is as follows: the level is inverted from high to low to represent 1, and from low to high to represent 0.

And judging a start frame by detecting the time count of edge conversion, recording the end position of the start frame, delaying 3/4 periods to wait for edge jump after the end position of the frame is determined, and recording a level signal after jump, wherein the signal after jump is the required RFID decoding data. The method only needs 1 timer, only needs to record the jump time, can greatly reduce the software overhead, and saves RAM and ROM.

The specific implementation method comprises the following steps:

let T0 be the period of the demodulated signal, T1 be the sampling period, and T1 be much smaller than T0, where 50 × T1 — T0 are set. The number of the start frames 1 is N.

1. Reading an initial frame:

the start frame is N1 s in succession, because the stop bit is 0, the start frame immediately following the stop bit is necessarily 1, and the first bit of the start frame is necessarily 1 transition, i.e., there are 2 × N-1 transition edges in N T0 cycles. And setting the effective jump time of the initial frame to be 20-30T 1-1, if jump is generated in the interval, adding 1 to the effective count of the initial frame, and otherwise, resetting the effective count of the initial frame. If the effective counting value of the initial frame is more than or equal to 2 × N-2, entering a data frame reading stage;

2. data frame reading:

after the initial frame is read, the data frame reading stage is directly started, the time is delayed 4/5 × T0, namely 40 × T1, the edge jump is waited, the level data after the jump is recorded, and the data counter is added with 1. If the data counter is more than or equal to 55 bits, the reading of the data frame is finished.

3. Parity check

To prevent data reception errors, parity checking is performed on the data frame. The fifth and tenth numbers of each row and column are parity check respectively. If the row and column check is passed, the RFID label is received correctly.

The codes corresponding to the steps are as follows:

1.1, start frame judgment code:

1.2 data frame judgment code

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A manchester encoding and decoding method, comprising the steps of:

s1, setting the period of the demodulation signal as T0, the sampling period as T1, and T0=50 × T1; reading a start frame, wherein the start frame is N1 continuous frames, because the stop bit is 0, the start frame immediately after the stop bit is 1, the first bit of the start frame is 1 jump, namely, in N T0 cycles, jump is necessary every 1/2 × T0, 2 × N-1 jump edges are provided, whether 2 × N-1 jumps exist is detected in N × T0 time, if yes, the start frame is judged to be correct, and then data is read and recorded;

the method for judging whether jumping exists comprises the following steps: setting the effective jumping time of the initial frame between 20 × T1 and 30 × T1, if jumping occurs in the interval, adding 1 to the effective count of the initial frame, otherwise, clearing the effective count of the initial frame;

and S3, checking whether the data reading is correct.

2. The manchester encoding and decoding method according to claim 1, wherein the specific steps in S2 are that, after the start frame is read, the data frame is directly read, the data frame is delayed by 4/5 × T0, namely 40 × T1, the edge jump is waited, the level data after the jump is recorded, and the data counter is incremented by 1; and if the data counter is more than or equal to 55 bits, the data frame is completely read.

3. The manchester encoding and decoding method of claim 1, wherein row-column parity or redundancy check is used in S3.

4. The manchester encoding and decoding method according to claim 3, wherein: the specific steps of carrying out parity check on the data frame are respectively parity check on the fifth number of each row and the tenth number of each column, and if the row and column check are passed, the RFID label is correctly received.