cancel
Showing results for 
Search instead for 
Did you mean: 

USB Superspeed Peripherals

Anonymous
Not applicable

Hello sir ,

               i have to generate a clock out pulse on fx3 pin using pwm of frequency 24 MHZ with 50% duty cycle for camera module ,also i have merged complexgpio example firmware with uvc .my question is in that complexgpio example they have set period  as (201600 - 1) and threshold as (50400  - 1). unable to understand how these values are taken.please help.

Thanks

Manisha

0 Likes
Reply
1 Solution
Moderator
Moderator

Hello Manisha,

The gpioConfig.period and gpioConfig.threshold parameters define the clock period and the PWM threshold value in terms of the timer ticks. In the case of GpioComplexApp example, these parameters are computed for a SYS_CLK frequency of 403.2MHz. Also, the complex GPIO clock is configured to run from the GPIO fast clock which is set to SYS_CLK/2. So, the value (20160-1) clock ticks would account for 100us and (5040-1) clock ticks would account for 25us. Below are the code statements that are responsible to arrive at this value and the calculation

  gpioClock.clkSrc = CY_U3P_SYS_CLK; // GPIO clock is derived from the SYS_CLK

gpioClock.fastClkDiv = 2;          // GPIO fast clock is configured for SYS_CLK/2

 

gpioConfig.timerMode = CY_U3P_GPIO_TIMER_HIGH_FREQ;     // Use the GPIO fast clock for generating the PWM

gpioConfig.period = CY_FX_PWM_PERIOD;     // Set the period to 20160 timer ticks

gpioConfig.threshold = CY_FX_PWM_25P_THRESHOLD;     // Set the threshold such that the duty cycle is 25%

Calculations:

SYS_CLK frequency = 403.2MHz

GPIO fast clock frequency = (SYS_CLK frequency)/2 = 201.6MHz

One clock period = 1/(GPIO fast clock frequency) = 1/201.6 us

PWM waveform period = (20160) * One clock period = 100 us

PWM threshold = (5040) * One clock period = 25us

Please let me know if you need further clarification.

Best regards,

Srinath S

View solution in original post

0 Likes
Reply
5 Replies
Moderator
Moderator

Hello Manisha,

The gpioConfig.period and gpioConfig.threshold parameters define the clock period and the PWM threshold value in terms of the timer ticks. In the case of GpioComplexApp example, these parameters are computed for a SYS_CLK frequency of 403.2MHz. Also, the complex GPIO clock is configured to run from the GPIO fast clock which is set to SYS_CLK/2. So, the value (20160-1) clock ticks would account for 100us and (5040-1) clock ticks would account for 25us. Below are the code statements that are responsible to arrive at this value and the calculation

  gpioClock.clkSrc = CY_U3P_SYS_CLK; // GPIO clock is derived from the SYS_CLK

gpioClock.fastClkDiv = 2;          // GPIO fast clock is configured for SYS_CLK/2

 

gpioConfig.timerMode = CY_U3P_GPIO_TIMER_HIGH_FREQ;     // Use the GPIO fast clock for generating the PWM

gpioConfig.period = CY_FX_PWM_PERIOD;     // Set the period to 20160 timer ticks

gpioConfig.threshold = CY_FX_PWM_25P_THRESHOLD;     // Set the threshold such that the duty cycle is 25%

Calculations:

SYS_CLK frequency = 403.2MHz

GPIO fast clock frequency = (SYS_CLK frequency)/2 = 201.6MHz

One clock period = 1/(GPIO fast clock frequency) = 1/201.6 us

PWM waveform period = (20160) * One clock period = 100 us

PWM threshold = (5040) * One clock period = 25us

Please let me know if you need further clarification.

Best regards,

Srinath S

View solution in original post

0 Likes
Reply
Anonymous
Not applicable

Thanks sir for your solution, but when I am setting value for system clock

384mhz period (192 -1) threshold for 50 %duty cycle (9600 -1) for 1mhz

frequency , getting 500khz frequency on oscilloscope . Can you please tell

what exactly the value for generating frequency in MHz .I want approx 10

MHz frequency for camera module.

Thanks

Manisha

0 Likes
Reply
Moderator
Moderator

Hello Manisha,

Please use the below configuration.

gpioClock.clkSrc = CY_U3P_SYS_CLK; // GPIO clock is derived from the SYS_CLK (403.2 MHz)

gpioClock.fastClkDiv = 2;          // GPIO fast clock is configured for SYS_CLK/2 (201.6 MHz)

gpioConfig.timerMode = CY_U3P_GPIO_TIMER_HIGH_FREQ;    // Use the GPIO fast clock for generating the PWM

gpioConfig.period = 20;    // Set the period to 20 timer ticks (20*1/201.6 us) ~= 0.1us -> 10 MHz

gpioConfig.threshold = 10;    // Set the threshold such that the duty cycle is 50%

Best regards,

Srinath S

0 Likes
Reply
Anonymous
Not applicable

Hello sir ,

Thanks for the solution. I have used system frequency as

384mhz and done calculations accordingly.But another problem I faced is in

my uvc code I have merged complexgpio pwm code .but only pwm code is

working and I am getting 10mhz frequency on gpio 50.can you please suggest

solution for it .

Thanks and regards

Manisha.

0 Likes
Reply
Moderator
Moderator

Hello Manisha,

I am not clear with your problem. Do you mean to say that when the complexgpio pwm code is integrated with the UVC application code, there is a problem. If yes, please mention the issue.

EDIT: Since this query is different from the one the thread was created for, it has been branched to a new thread.

Best regards,

Srinath S

0 Likes
Reply