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Hi,
I would like to use the PrISM component to change the brightness of a led Matrix.
I have configured the PrISM component with a resolution of 8 bits, the pulse density type as Less Than or Equal.
To change the dimming value, I modify the pulse density with the API function PWM_L_WritePulse0(item), sending and integer from 0 to 255. The dimming is working but is not linear.
I have the following curve:
How can I make the dimming linear?
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hello,
I suspect that non-linearity comes from rise-time characteristics of the LED. To test, try reducing PrISM clock frequency; also try PWM instead of PrISM. The issue with PrISM is very high bandwidth, some devices with input threshold may not respond to short pulses correctly due to not fully opening. While using PrISM seems attractive, it's time profile shows occasional long peaks/valleys, changing unpredictably from one PrISM code to another. The LED responds mostly to long peaks/valleys, which becomes non-linear.
/odissey1
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Hello,
Can you tell which PSoC device ae you using? For PSoC 1 the following application note is available for LED Dimming:
https://www.cypress.com/file/133251/download
Regards
Ekta
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Hi,
I'm using a PSoC 4200L CY8C4246AZI-L433
Regards
Norman
Le lun. 18 mars 2019 à 10:14, EktaN_26 <community-manager@cypress.com> a
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Understanding PrISM
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<https://community.cypress.com/message/190208?et=watches.email.thread#190208>
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Hello.
Did you try reducing the PrISM clock frequency to achieve linear dimming?
Regards
Ekta
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Hi,
Yes I have reduce the clock frequency, and i the dimming is more linear, I
have also tried the PWM component and the output is perfectly linear.
Still i don't get why PrISM does not work, it is suppose be used for this
kind of application:
The PrISM component provides modulationtechnology that significantly
reduces low-frequency flicker and radiated electromagnetic interference
(EMI),which are common problems with high- brightness LED designs.
Regards
Norman
Le mar. 26 mars 2019 à 01:14, EktaN_26 <community-manager@cypress.com> a
écrit :
<http://www.cypress.com>
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<https://community.cypress.com/?et=watches.email.thread>
Understanding PrISM
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<https://community.cypress.com/message/190802?et=watches.email.thread#190802>
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Hello Norman,
I just wanted to know that, how are you measuring whether the dimming is linear or not?
Regards,
Ekta