Infineon CCU6 PWM Capture 1 User manual

AURIX™ TC2xx Microcontroller Training
V1.0.0
CCU6_PWM_Capture_1
CCU6 PWM signal capture
Please read the Important Notice and Warnings at the end of this document

Scope of work
The CCU6 unit is used to capture an external PWM signal and calculate
its frequency and duty cycle.
A simple PWM signal is generated by toggling a port pin. The resulting PWM
frequency and duty cycle is measured by the Capture/Control Unit 6 (CCU6).
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Introduction
›The Capture/Compare Unit 6 (CCU6) is a high resolution 16 bit capture
and compare unit specially designed for motor control purposes.
›The CCU6 unit is made up of a timer T12 Block with three
capture/compare channels and a timer T13 Block with one compare
channel.
›Among other features, the CCU6 has the capability to capture external
input signals. In this example, the Input Capture Unit and the timer T12 of
the CCU6 module are used to capture a PWM signal and calculate its
frequency and duty cycle.
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Hardware setup
This code example has been developed
for the board
KIT_AURIX_TC297_TFT_BC-Step.
Connect the two pins
P02.1 (PWM signal) and P02.0
(CC60 input) to each other.
PWM signalinput pin A
of CC60
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Implementation
Configuring the CCU6 Input Capture Unit
To properly configure the CCU6 module for capturing a PWM signal, the module itself
and one of its channels need to be configured.
For the configuration of the module, the following steps are required:
›An instance of the structure IfxCcu6_Icu_Config needs to be created and default
values are assigned to the configuration with the function
IfxCcu6_Icu_initModuleConfig()
›For capturing a PWM signal, no changes to the default configuration are required,
therefore the module can be initialized with the default configuration by calling the
function IfxCcu6_Icu_initModule()
›After the successful initialization of the CCU6 module, its handle structure
(IfxCcu6_Icu) contains the configured capture frequency of the timer. For further
usage, this parameter is stored in the global variable
g_CCU6captureFrequency_Hz.
All used functions and structures can be found in the iLLD header IfxCcu6_Icu.h.
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Implementation
Configuring the CCU6 Input Capture Unit
For the configuration of the channel, an instance of the structure IfxCcu6_Icu_ChannelConfig
is created and default values are assigned to the configuration with the function
IfxCcu6_Icu_initChannelConfig(). Then, the following changes to the default configuration are
required:
›channelld –Select the channel of timer T12. In this example, channel 0 is selected
›channelMode –Select the operating mode for the channel. In this example, the rising and
falling edges of an external signal are captured using the double register capture mode
›Interrupt1 structure –Configure an interrupt by selecting the source, the service request
output, its priority and the service provider. In this example, the CCU6 service request 0 is
configured to trigger an interrupt on every rising edge at the input pin of capture/compare
channel 0 (CC60). To calculate the duty cycle, a shadow register filled when a falling edge
occurs, is used. Therefore, no interrupt is required for the falling edge.
›Interrupt2 structure –Configure another interrupt similar with the previous, where the CCU6
service request 1 is configured to trigger an interrupt on every period match (match of the
timer T12 counter value with the period value)
Note: An interrupt is needed to capture the PWM frequency, while the other counts the number
of timer overflows (for more details, see slides 8-12).
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Implementation
Configuring the CCU6 Input Capture Unit
›trigger.extInputTrigger - Select the internal start controlled by the run bit T12R
by setting a null pointer (NULL_PTR) to this field
›pins –A structure to set the used port pins for the CCU6 configuration. Only
CC60In with input mode IfxPort_InputMode_pullUp is selected
›multiInputCaptureEnabled –Disable the multiple input capture mode
After the initialization of the channel with the user configuration (which is applied by
calling the function IfxCcu6_Icu_initChannel()), the capture process is started by
setting the run bit T12R through the function IfxCcu6_Icu_startCapture().
All functions and structures used for the configuration of the CCU6 channel can be
found in the iLLD header IfxCcu6_Icu.h.
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Implementation
The Interrupt Service Routines (ISR)
For capturing of PWM signals with the CCU6 module, two ISRs are required:
›CCU6_ICU_Period_Match_Int_Handler() - Interrupt on every period
match, used for counting the timer overflows
›CCU6_ICU_Rising_Edge_Int_Handler() - Interrupt on every rising edge
at the input pin of capture/compare channel 0, used to calculate
–the time between two rising edges and the PWM frequency
–the time between a rising edge and the falling edge and the PWM duty
cycle
The method implementing each ISR needs to be assigned a priority and a
CPU core responsible for its execution. This is done with the macro
IFX_INTERRUPT(isr, vectabNum, priority).
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Implementation
The Interrupt Service Routines (ISR)
›When the rising edge is detected at the input pin of capture/compare channel 0 (CC60), the
interrupt handler (CCU6_ICU_Rising_Edge_Int_Handler()) is triggered
›The interrupt status flags of the CC60 interrupt have to be cleared inside the ISR
›The PWM frequency is calculated by dividing the CCU6 capture frequency
(g_CCU6captureFrequency_Hz) by the total amount of increments of the timer T12 (the
time between two rising edges)
›The PWM duty cycle is calculated as a percentage value between the amount of increments
of the timer T12 between the rising and falling edge (high level time) and the total amount of
increments between two rising edges (period).
›An overflow of timer T12 triggers the second interrupt
(CCU6_ICU_Period_Match_Int_Handler()) which is used for counting:
–the overflows between two rising edges for PWM frequency calculation
–the overflows between the rising edge and the falling edge for PWM duty cycle calculation
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Implementation
Calculation example of the PWM frequency
Background knowledge:
›Maximum value of timer T12 is 65534 (16 bit –1; default configuration, configured inside
function IfxCcu6_Icu_initModuleConfig())
›Frequency of timer T12 is 781250 Hz (stored inside variable
g_CCU6captureFrequency_Hz; default configuration), which means that the value of timer
T12 is incremented every 1.28 µs (1 / 781250 Hz)
›Overflow of timer T12 occurs after ≈ 0.084 s(65534 * 1.28 µs)
›The total amount of increments can be calculated by comparing the current value of timer
T12 with the value of timer T12 one PWM period ago e.g. 1000
Interrupt on each rising edge:
T12 count
(value is incremented
with frequency of timer T12)
PWM signal
t
t
Period of
timer T12 overflow
Period of
PWM signal High level
time
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Implementation
Calculation example of the PWM frequency
Example for 2 Hz PWM signal with 50% duty cycle:
›Period time of 2 Hz signal is 0.5 s
›High level time is 0.25 s (period * duty cycle)
›Within 0.5 s, the timer T12 is incremented 390625 times (0.5 s / 1.28 µs) and has 5overflows
›Within 0.25 s, the timer T12 is incremented 195312 times (0.25 s / 1.28 µs) and has 2overflows
›Parameters available inside the ISR:
–Counter value of timer T12 one period ago: 1000
–Current counter value of timer T12: 63955
–Counter value when the falling edge occured: 65244
–Amount of overflows during one PWM period: 5
–Amount of overflows during PWM high level time: 2
›Calculation of total amount of increments:
–Increments before the first overflow: 65534 –1000 = 64534
–Increments during the second and the last overflow: (5 - 1) * 65534 = 262136
–Increments after the last overflow: 63955
–Total amount of increments: 64534 + 262136 + 63955 = 390625
›Calculation of increments during high level time:
–Increments before the first overflow: 65534 –1000 = 64534
–Increments during the second and the last overflow: (2 - 1) * 65534 = 65534
–Increments after the last overflow: 65244
–Total amount of increments: 64534 + 65534 + 65244 = 195312
›Calculation of the PWM frequency by dividing the frequency of timer T12 by the total amount of
increments during one PWM period:
–781250 Hz / 390625 = 2 Hz
›Duty cycle (increments during high level time / increments during total period) = 195312 / 390625 = 50%
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Implementation
Period calculation example
›Part 1: 64534 increments before the first overflow: 65534 -1000 = 64534
(Maximum value of T12 - counter value at rising edge = total increments)
›Part 2: 262136 increments between the first and last overflow:
4 * 65534 = 262136 (4 overflows * maximum value of T12 = total increments)
›Part 3: 63955 increments after the last overflow: 63955 (counter value at rising edge)
›Total increments between two rising edges: 64534 + 262136 + 63955 = 390625
T12 count
(between 0 and 65534)
PWM signal (2 Hz)
Period of PWM signal 0.5 s
t
t
Interrupt on previous rising edge
T12 counter value: 1000 T12 counter value: 63955
Interrupt on current rising edge
5 overflows of timer T12 during one
PWM period
Part 1 Part 2 Part 3
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Implementation
High Level time calculation example
›Part 1: 64534 increments before the first overflow: 65534 -1000 = 64534
(Maximum value of T12 - counter value at rising edge = total increments)
›Part 2: 65534 increments between the first and last (before falling edge) overflow:
1 * 65534 = 65534 (1 overflows * maximum value of T12 = total increments)
›Part 3: 63955 increments after the last overflow: 63955 (counter value at rising edge)
›Total increments between the rising and falling edges: 64534 + 65534 + 65244 =
195312
T12 count
(between 0 and 65534)
PWM signal (2 Hz)
Period of PWM signal 0.5 s
t
t
Interrupt on previous rising edge
T12 counter value: 1000 T12 counter value: 65244
Interrupt on current rising edge
2 overflows of timer T12 during high level time
Part 1 Part 2 Part 3
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Implementation
Generation of PWM signal
After initializing the time constants (initTime()) and setting the port pin P02.1 as
push-pull output (IfxPort_setPinMode()), a simple PWM signal is generated by
toggling a pin with the function generate_PWM_signal().
The state of the output port pin P02.1 is toggled by calling the function
IfxPort_setPinState() with the parameters IfxPort_State_high and
IfxPort_State_low.
For changing the frequency and duty cycle of the generated PWM signal the global
parameter g_generatedPwmFreq_Hz and g_generatedDutyCycle can be modified.
Depending on the frequency and duty cycle (set to 50%), two timeout values are
calculated by software and passed to the wait() function. The two wait() function calls
are succeeding the two calls of the function IfxPort_setPinState().
The parameters and functions used for the port pin control and timing are provided by
the two iLLD headers IfxPort.h and Bsp.h.
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Run and Test
After code compilation and flashing the device, perform the following steps:
1. Connect the two pins P02.1 (PWM signal) and P02.0 (CC60 input) to each other
2. Check the parameter g_measuredPwmFreq_Hz in the debugger (the debug
session should be suspended previously). Its value should be similar to the
parameter g_generatedPwmFreq_Hz
3. Change the parameter g_generatedPwmFreq_Hz and check if
g_measuredPwmFreq_Hz changes accordingly
4. Check the parameter g_measuredPwmDutyCycle in the debugger (the debug
session should be suspended previously). Its value should be similar to the
parameter g_generatedPwmDutyCycle
5. Change the parameter g_generatedDutyCycle and check if
g_measuredDutyCycle changes accordingly
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References
›More code examples can be found on the GIT repository:
›https://github.com/Infineon/AURIX_code_examples
›For additional trainings, visit our webpage:
›https://www.infineon.com/aurix-expert-training
›AURIX™ Development Studio is available online:
›https://www.infineon.com/aurixdevelopmentstudio
›Use the „Import...“ function to get access to more code examples.
›For questions and support, use the AURIX™ Forum:
›https://www.infineonforums.com/forums/13-Aurix-Forum
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IMPORTANT NOTICE
The information given in this document shall in no
event be regarded as a guarantee of conditions or
characteristics (“Beschaffenheitsgarantie”).
With respect to any examples, hints or any typical
values stated herein and/or any information
regarding the application of the product, Infineon
Technologies hereby disclaims any and all
warranties and liabilities of any kind, including
without limitation warranties of non-infringement
of intellectual property rights of any third party.
In addition, any information given in this
document is subject to customer’s compliance
with its obligations stated in this document and
any applicable legal requirements, norms and
standards concerning customer’s products and
any use of the product of Infineon Technologies in
customer’s applications.
The data contained in this document is exclusively
intended for technically trained staff. It is the
responsibility of customer’s technical
departments to evaluate the suitability of the
product for the intended application and the
completeness of the product information given in
this document with respect to such application.
For further information on the product,
technology, delivery terms and conditions and
prices please contact your nearest Infineon
Technologies office (www.infineon.com).
WARNINGS
Due to technical requirements products may
contain dangerous substances. For information
on the types in question please contact your
nearest Infineon Technologies office.
Except as otherwise explicitly approved by
Infineon Technologies in a written document
signed by authorized representatives of Infineon
Technologies, Infineon Technologies’ products
may not be used in any applications where a
failure of the product or any consequences of the
use thereof can reasonably be expected to result
in personal injury.
Edition 2020-01
Published by
Infineon Technologies AG
81726 Munich, Germany
© 2020 Infineon Technologies AG.
All Rights Reserved.
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Document reference
CCU6_PWM_Capture_1
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