CN104796118B - A kind of limitation output pwm of breakthrough MCU hardware method - Google Patents
A kind of limitation output pwm of breakthrough MCU hardware method Download PDFInfo
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- CN104796118B CN104796118B CN201510211221.8A CN201510211221A CN104796118B CN 104796118 B CN104796118 B CN 104796118B CN 201510211221 A CN201510211221 A CN 201510211221A CN 104796118 B CN104796118 B CN 104796118B
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Abstract
The invention discloses a kind of limitation output pwm of breakthrough MCU hardware method, it is characterised in that comprises the following steps：S1, initialization clock configuration, the continuous clock that one 8 are configured in MCU overflow interruption；, after the time of setting, there is an interruption in S2, normal operation；And S3, judge whether I/O output identifications are true, when I/O output identifications are true, low level time is to clock timer in heavily loaded pwm, and I/O output identifications are set to false, and I/O mouthful export low levels, then repeat step S2；High level time is to clock timer in I/O output identifications are fictitious time, heavily loaded pwm, and I/O output identifications are set to true, I/O mouthfuls of output high level, then repeat step S2.The product up-gradation construction cycle is short, it is not necessary to changes hardware circuit, addition high speed outer crystal oscillator or changes high speed MCU, reduces cost.
Description
Technical field
The present invention relates to the method in pulsewidth modulation field, more particularly to a kind of limitation output pwm of breakthrough MCU hardware.
Background technology
MCU perfect in shape and function in current various electronic equipments, wherein just comprising pwm output functions；Its MCU hardware supported
Pwm output function, it is only necessary to which pwm configurations are carried out to current MCU, you can obtain the pwm outputs of corresponding frequency.
But the frequency of MCU hardware pwm outputs is limited for the MCU crystal oscillators selected and electronic circuit, in order to carry
The frequency of high pwm output, existing technology has three kinds：
（1）Hardware circuit is changed, pwm delivery outlets are changed to the outlet of other pwm function numbers.Defect is：Product up-gradation is more
Change circuit and software to carry out simultaneously, the upgrading construction cycle is long, and negative value is more；
（2）High speed outer crystal oscillator is added, makes the increase of pwm output frequencies.Defect is：It need to upgrade circuit and most of software is matched somebody with somebody
Put, the upgrading construction cycle is long, product cost rise, negative value is more；
（3）Change more high speed MCU.Defect is：Product cost is raised, and software is developed again, and the cycle is long.
The content of the invention
It is an object of the invention to provide a kind of breakthrough MCU hardware limitation output pwm method, increase hardware unit and
Pwm output frequencies are lifted in the case of circuit structure.
The technical scheme is that a kind of limitation output pwm of breakthrough MCU hardware method, comprises the following steps：
S1, initialization clock configuration, the continuous clock that one 8 are configured in MCU overflow interruption；
, after the time of setting, there is an interruption in S2, normal operation；And
S3, judge whether I/O output identifications are true, when I/O output identifications are true, low level time is given in heavily loaded pwm
Clock timer, I/O output identifications are set to false, I/O mouthfuls of output low levels, then repeat step S2；When I/O output identifications are false
When, high level time is to clock timer in heavily loaded pwm, and I/O output identifications are set to true, I/O mouthfuls of output high level, then repeats
Step S2.
The technical program carries out simulation pwm output functions using 8 bit clock timers so that can by I/O mouthfuls in MCU
Dutycycle number Dc is adjusted to carry out any setting.Such as by Dc=100, then Dc<255 ；So that frequency is raised, breach original
The pwm output functions of MCU hardware.The product up-gradation construction cycle is short, it is not necessary to change hardware circuit, addition high speed outer crystal oscillator
Or high speed MCU is changed, reduce cost.
Further, in step S2, the time of the setting meets following formula：
Tx=255*t
In formula, Tx represents the time apart from next interruption, and t represents MCU instruction cycle.Program runs to time Tx
When, there is an interruption；When off-duty is to Tx, continue to run with.
Further, in step S3, low level time meets following formula in heavily loaded pwm：
Tl=（255-Dc+Dd）*t
In formula, Tl represents low level time in pwm, and t represents MCU instruction cycle, and Dc represents adjustable duty cycle number,
Dd represents the corresponding numerical value of dutycycle.
Further, in step S3, high level time meets following formula in heavily loaded pwm：
Th=（255-Dd）*t
In formula, Th represents high level time in pwm, and t represents MCU instruction cycle, and Dd represents the corresponding number of dutycycle
Value.
Further, the pwm waveforms that the MCU I/O mouths final output stable cycle is T, the cycle T meets formula：
T=Th+Tl=Dc*t （1）
In formula, T represents pwm cycle, and t represents the MCU instruction cycles, and Dc represents adjustable duty cycle number；
The dutycycle of the pwm waveforms is（Dd/Dc）*100%；
According to formula（1）It can draw, the frequency of MCU I/O mouth final output pwm waveforms meets formula：
Fpwm=1/T=1/(Dc*t)
In formula, Dc represents adjustable duty cycle number, and t represents MCU instruction cycle
Beneficial effect：Simulation pwm output functions are carried out by using 8 bit clock timers so that can be by I/O in MCU
Mouth adjustable duty cycle number Dc carries out any setting so that frequency is raised, and breaches the pwm output works of original MCU hardware
Energy.The product up-gradation construction cycle is short, it is not necessary to changes hardware circuit, addition high speed outer crystal oscillator or changes high speed MCU, reduces
Cost.
Brief description of the drawings
Fig. 1 is the workflow diagram of an embodiment of the present invention.
Embodiment
Below in conjunction with the accompanying drawings, the preferably embodiment to the present invention is described in further detail：
Referring to Fig. 1, a kind of limitation output pwm of breakthrough MCU hardware method comprises the following steps：
S1, initialization clock configuration, the continuous clock that one 8 are configured in MCU overflow interruption；
, after the time of setting, there is an interruption in S2, normal operation；And
S3, judge whether I/O output identifications are true, when I/O output identifications are true, low level time is given in heavily loaded pwm
Clock timer, I/O output identifications are set to false, I/O mouthfuls of output low levels, then repeat step S2；When I/O output identifications are false
When, high level time is to clock timer in heavily loaded pwm, and I/O output identifications are set to true, I/O mouthfuls of output high level, then repeats
Step S2.
In step S2, the time of the setting meets following formula：
Tx=255*t
In formula, Tx represents the time apart from next interruption, and t represents MCU instruction cycle.Program runs to time Tx
When, there is an interruption；When off-duty is to Tx, continue to run with.
In step S3, low level time meets following formula in heavily loaded pwm：
Tl=（255-Dc+Dd）*t
In formula, Tl represents low level time in pwm, and t represents MCU instruction cycle, and Dc represents adjustable duty cycle
Number, Dd represents the corresponding numerical value of dutycycle.
In step S3, high level time meets following formula in heavily loaded pwm：
Th=（255-Dd）*t
In formula, Th represents high level time in pwm, and t represents MCU instruction cycle, and Dd represents the corresponding number of dutycycle
Value.
The pwm waveforms that the MCU I/O mouths final output stable cycle is T, the cycle T meets formula：
T=Th+Tl=Dc*t （1）
In formula, T represents pwm cycle, and t represents the MCU instruction cycles, and Dc represents adjustable duty cycle number；
The dutycycle of the pwm waveforms is（Dd/Dc）*100%；
According to formula（1）It can draw, the frequency of MCU I/O mouth final output pwm waveforms meets formula：
Fpwm=1/T=1/(Dc*t)
In formula, Dc represents adjustable duty cycle number, and t represents MCU instruction cycle.
In the present embodiment, MCU model MB95F564K, t=0.25, it is assumed that Dd=50, Dc=100, then pwm waveforms are accounted for
Empty ratio is：
50/100*100=50%,
The frequency of MCU I/O mouth final output pwm waveforms is：
(1/100*0.25)MHz=40KHz。
Therefore, it is assigned to Dd by 50 in software, so that it may so that it is 50% that the MCU, which exports 40KHz dutycycle,
Pwm waveforms.
The present embodiment carries out simulation pwm output functions using 8 bit clock timers so that can be adjustable by I/O mouthfuls in MCU
Dutycycle number Dc carries out any setting.Such as by Dc=100, then Dc<255 ；So that frequency is raised, original MCU is breached
The pwm output functions of hardware.The product up-gradation construction cycle is short, it is not necessary to change hardware circuit, addition high speed outer crystal oscillator or more
High speed MCU is changed, cost is reduced.
Above content is to combine specific preferred embodiment further description made for the present invention, it is impossible to assert
The specific implementation of the present invention is confined to these explanations.For general technical staff of the technical field of the invention,
On the premise of not departing from present inventive concept, some simple deduction or replace can also be made, should all be considered as belonging to the present invention's
Protection domain.
Claims (4)
1. the limitation output pwm of a kind of breakthrough MCU hardware method, it is characterised in that comprise the following steps：
S1, initialization clock configuration, the continuous clock that one 8 are configured in MCU overflow interruption；
, after the time of setting, there is an interruption in S2, normal operation；And
S3, judge whether I/O output identifications are true, when I/O output identifications are true, low level time is to clock in heavily loaded pwm
Timer, I/O output identifications are set to false, I/O mouthfuls of output low levels, then repeat step S2；When I/O output identifications be fictitious time,
High level time is to clock timer in heavily loaded pwm, and I/O output identifications are set to true, I/O mouthfuls of output high level, then repeats to walk
Rapid S2；
In step S3, low level time meets following formula in heavily loaded pwm：
Tl=（255-Dc+Dd）*t
In formula, Tl represents low level time in pwm, and t represents MCU instruction cycle, and Dc represents adjustable duty cycle number, Dd tables
Show the corresponding numerical value of dutycycle.
2. the limitation output pwm of breakthrough MCU hardware according to claim 1 method, it is characterised in that in step S2,
The time of the setting meets following formula：
Tx=255*t
In formula, Tx represents the time apart from next interruption, and t represents MCU instruction cycle.
3. the limitation output pwm of breakthrough MCU hardware according to claim 2 method, it is characterised in that in step S3,
High level time meets following formula in heavily loaded pwm：
Th=（255-Dd）*t
In formula, Th represents high level time in pwm, and t represents MCU instruction cycle, and Dd represents the corresponding numerical value of dutycycle.
4. the limitation output pwm of breakthrough MCU hardware according to claim 3 method, it is characterised in that MCU I/O mouths
The pwm waveforms that the final output stable cycle is T, the cycle T meets formula：
T=Th+Tl=Dc*t （1）
In formula, T represents pwm cycle, and t represents the MCU instruction cycles, and Dc represents adjustable duty cycle number；
The dutycycle of the pwm waveforms is（Dd/Dc）*100%；
According to formula（1）It can draw, the frequency of MCU I/O mouth final output pwm waveforms meets formula：
Fpwm=1/T=1/(Dc*t)
In formula, Dc represents adjustable duty cycle number, and t represents MCU instruction cycle.
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| CN105446417B (en) * | 2014-08-21 | 2018-07-27 | Tcl集团股份有限公司 | A kind of method and system obtaining high precision timing signal |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6995592B2 (en) * | 2003-11-06 | 2006-02-07 | Stmicroelectronics Pvt. Ltd. | Method and system for generating variable frequency cyclic waveforms using pulse width modulation |
| CN1996729A (en) * | 2006-12-23 | 2007-07-11 | 深圳市拓邦电子科技股份有限公司 | Multi-channel PWM generation system and method |
| US7348755B2 (en) * | 2003-12-18 | 2008-03-25 | The Boeing Company | Time sliced DSP operation for very high frequency pulse width modulated controllers |
| CN103312300A (en) * | 2013-06-24 | 2013-09-18 | 哈尔滨工业大学 | Pulse-width modulation (PWM) signal generator based on field programmable gate array (FPGA) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1653618A3 (en) * | 2004-10-29 | 2008-05-28 | STMicroelectronics Pvt. Ltd. | A PWM generator providing improved duty cycle resolution |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6995592B2 (en) * | 2003-11-06 | 2006-02-07 | Stmicroelectronics Pvt. Ltd. | Method and system for generating variable frequency cyclic waveforms using pulse width modulation |
| US7348755B2 (en) * | 2003-12-18 | 2008-03-25 | The Boeing Company | Time sliced DSP operation for very high frequency pulse width modulated controllers |
| CN1996729A (en) * | 2006-12-23 | 2007-07-11 | 深圳市拓邦电子科技股份有限公司 | Multi-channel PWM generation system and method |
| CN103312300A (en) * | 2013-06-24 | 2013-09-18 | 哈尔滨工业大学 | Pulse-width modulation (PWM) signal generator based on field programmable gate array (FPGA) |
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Address after: 518000 Guangdong province Shenzhen Guangming New District Gongming street Gongming South Avenue Geya Technology Building 3 building 1-4 layer Patentee after: Shenzhen Zhenbang intelligent Polytron Technologies Inc Address before: 518000 Guangdong, Nanshan District, Taoyuan, Longjing street, industrial zone, building A, building 2, building A, building on the ground floor, building B, building, building 6, building C, block B, building, building No. 3 Patentee before: SHENZHEN ZHENBANG INTELLIGENT TECHNOLOGY CO., LTD. |
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