You are here

Setting Slew Rate with Analog Issues | Cypress Semiconductor

Setting Slew Rate with Analog Issues

Summary: 9 Replies, Latest post by Tfuk on 24 Nov 2014 03:34 PM PST
Verified Answers: 0
Last post
Log in to post new comments.
user_385042613's picture
7 posts

Okay, i am enjoying very much the PSoC architecture.

Now im doing a little project and i got this issue.

This is the configuration:


I want the digital outputs SSRx to be Slow Slewrate, so i try this procedure:

1) Configure the outputs with Slow SlewRate;

Result: the compiler blaims that the analogs I/Os in the same ports (P1 and P2) are configured as Fast SlewRate (default)

2) I go to each this analog I/Os (ADC0, ColdRef and MuxOut), enable it as digital output, configure as Slow SlewRate, disable the Digital Output and apply;

Result: the compiler dont blame about the analog I/Os that i made the changes; but it blames about the SAR ByPass (P1.7) configured as Fast I/O;

3) I try to change the setting for the SAR ByPass, but it is a "part from the PSoC Creator install and changes cannot be saved";


So here are the questions:

1) If i could change the "output" setting of the SAR ByPass to Slow Slewrate (event it being an analog input), could i have those outputs as Slow Slewrate ?

2) How can i change the settings of the SAR ByPass to Slow Slewrate?

3) Why i need to change the digital output settings of analog input that are not configured as digital outputs ? Is that a PSoC creator issue ? Why there isnt a "button" to put all the pins in the port as Slow Slewrate and overwrite any analog input configuration ?



Thanks in advance!

user_1377889's picture
9296 posts

Welcome in the fascinating world of PSoCs!

It is much easier for us when we can play with your project in the IDE to answer your questions. Can you post your complete project, so that we all can have a look at all of your settings? To do so, use
Creator->File->Create Workspace Bundle (minimal)
and attach the resulting file. Helpfull, too is when you tell us whether you use your own board or a development kit and which one.


user_385042613's picture
7 posts

Okay Bob,


now a simplier version:

It builds okay as it is: Output of Pin1_Analog as default (Fast), Pin3_Fast in the same port configured as Fast Slewrate and Pin2_Slow configured as Slow SlewRate but in another port.

Now i figured out that isnt a simple question of changing the ByPass to Slow Output.

Without the ByPass cap of the ADC, if i try to change the Pin3_Fast to Slow slewrate, i need also do the trick of changing the Analog Input to Slow Slewrate. Then the compiler dont blame about it. But the analog router is "Unable to find a solution for the analog routing".


So, maybe there is a hardware limitation where i cannot have analog Input with a Slow Slewrate output in the same port ?



user_1377889's picture
9296 posts

When looking into the datasheet for the pin-component you will see that the pin's slew rate only applies for a digital output.

For an analog pin you cannot set a slew-rate.


The question that remains is: What would you like to perform by plying with the slew-rate? What do you expect to happen?



user_385042613's picture
7 posts

> The question that remains is: What would you like to perform by plying with the slew-rate? What do you expect to happen?


I want to set the SlewRate of the output to Slow in a Port that have an analog input.


In my research in documentation and thoughts, i saw no reason to an analog input pin configured in a port imples that this port obligatory has to be set to Fast SlewRate output type.


The messy part is that PSoC Creator didnt deal with this case clearly: it allows me to tricky change the "output slewrate" property of analog inputs, even without making much sense. Then when all the slewrates of the port are the same, it cant generate the solution for the analog part.


So i dont know if its a hardware issue (analog input only works for a port configured with Fast SlewRate) or a software issue (PSoC Creator is unable to deal with this situation yet).


user_1377889's picture
9296 posts

Excerpt from datasheet "Pins 2.5" page 15

Output Subtab
The Output subtab specifies output settings. If the pin type is not Digital Output or
Bidirectional this tab is disabled because you do not need to specify output information.
 Slew Rate – The slew rate parameter determines the rise and fall ramp rate for the pin as
it changes output logic levels. Fast mode is required for signals that switch at greater than
1 MHz. You can select slow mode for signals less than 1 MHz switching rate and benefit
from slower transition edge rates, which reduce radiated EMI and coupling with
neighboring signals. On PSoC 4, all pins on the same port must have the same Slew

user_14586677's picture
7646 posts

You might consider filing a CASEand posting answer back here -





/* Style Definitions */
{mso-style-name:"Table Normal";
mso-padding-alt:0in 5.4pt 0in 5.4pt;
mso-fareast-font-family:"Times New Roman";
mso-bidi-font-family:"Times New Roman";

To create a technical or issue case at Cypress -


“Technical Support”

“Create a Case”


You have to be registered on Cypress web site first.


Regards, Dana.


Stub for 440443488's picture
1 post

Okay, done the "Case". As soon i get the answer, i will post it here



user_1377889's picture
9296 posts

Your given Example1 compiles without errors or warnings (just one note) with Creator 3.0 SP2.



user_385042613's picture
7 posts



> Your given Example1 compiles without errors or warnings (just one note) with Creator 3.0 SP2.


The problem was to change Pin_3_Fast to Slow Slewrate Output.


The Cypress Team answer to the case:

"It seems to that problem with PSoC Creator and I am checking with Software team.

However, to use slew rate digital with analog pin on same port, just enable digital output of analog pin and set slow slew rate for that pin also.(figure.png)."


Then it builds.

Think i gonna have to use


in the initialization to configure the I/O, as the documentation says (AN86439, PSoC ® 4 – Using GPIO Pins, page 18)


Log in to post new comments.