cancel
Showing results for 
Search instead for 
Did you mean: 

PSoC 5, 3 & 1 MCU

Anonymous
Not applicable
        Hi there....I am giving a 10KHz clock to two pins of PSoC3 kit : P1[2] and P3[2]. Both have been configured in the schematic as "DIGITAL OUTPUT" pins...... When I check the output on a CRO, I get square waves [as expected] ...BUT the amplitude of both the waves is different.............it is around 3 volts for P1[2] and around 4.4volts for P3[2]. ........................my VDDD is 3.3 and VDDA is 5. ------------------------------------------------------------------------------------------------------------------- NOW, http://www.cypress.com/?docID=42947 This link suggests that Port 3 should be used as analog while Port 1as digital......SO this might explain it.............. But I have "configured" the pins as "DIGITAL" OUTPUT . So why varying amplitudes???   
0 Likes
Reply
1 Solution
Honored Contributor II

The reason is that the different IO ports are bound to different voltage rails. Have a look at the schematic for the -030 kit. It shows that Vddio1 and Vddio2 are connected to Vddd (the digital rail), while Vddio3 and Vddio0 are connected to Vdda (the analog rail).

   

Port P3[3] is powered by Vddio3, which is set to 5V. Port P1[2] is powered by Vddio1, which is set to 3.3V. So everything is how it should be 🙂

   

Remember: Computers to what you tell them, not what you want them to do...

View solution in original post

0 Likes
Reply
11 Replies
Esteemed Contributor II

WHICH PSoC3 kit are you using? a FirstTouch, a -030 or a -001. I'd like to have a look into the schematic.

   

 

   

Bob

0 Likes
Reply
Anonymous
Not applicable
        I am using -030. Also I have set the jumper settings to be 5V analog...3.3 Digital.   
0 Likes
Reply
Honored Contributor II

The reason is that the different IO ports are bound to different voltage rails. Have a look at the schematic for the -030 kit. It shows that Vddio1 and Vddio2 are connected to Vddd (the digital rail), while Vddio3 and Vddio0 are connected to Vdda (the analog rail).

   

Port P3[3] is powered by Vddio3, which is set to 5V. Port P1[2] is powered by Vddio1, which is set to 3.3V. So everything is how it should be 🙂

   

Remember: Computers to what you tell them, not what you want them to do...

View solution in original post

0 Likes
Reply
Esteemed Contributor

I had no ideas that I was the cause of my own design/debugging issues and problems !

   

Very disturbing disclosure Hli.....

   

 

   

Regards, Dana.

0 Likes
Reply
Honored Contributor II
        This is my golden rule for debugging problems: always assume its your own fault.   
Its true for maybe 95% of the time, and saves much of my time (and public embarrassment too...)   
0 Likes
Reply
Anonymous
Not applicable

ok.......i always thought that setting the jumper settings to 3.3 digital would mean that the kit will always give 3.3 volt for digital cases.

   

But with the ports behaving as analog and digital, it gets possible to achieve even 5v digital [even with 3.3 jumper settings]....

   

.

   

good versatality.........will prove useful in some cases!!!

   

 

   

Thanks !!!!!

0 Likes
Reply
Honored Contributor II
        This actually is a (mis-?)feature of the board, not of PSoC.   
PSoC has the notion of analog supply, digital supply and IO supply voltages. The analog supply powers all analog components, and the digital supply all the digital components.   
Then there are four different IO banks, each of which can be powered by a separate voltage. Now the design of the -030 kit is so that 3 banks are powered by the analog supply voltage, and the other two by the digital supply voltage.   
So this can be misleading if one doesn't deeply look at the schematic of the board.   
I think it is good practice with the kits to set analog and digital voltage to the same value all the time. This will avoid confusions. Only when designing your own board one should look at which IO bank should have a different voltage (or if you have a very good reason to do so with the kit, and understand what you are doing).   
Also, it might be good if Cypress extends the kit documentation to explain this feature in a prominent place to avoid such confusions.   
Esteemed Contributor

PSOC 3 Power Domains -

   

 

   

0 Likes
Reply
Anonymous
Not applicable

@Goose,

   

You should raise a support case so they can put a bug fix request to the team

0 Likes
Reply
Anonymous
Not applicable

I agree..the kit documentation should be modified to explain this thing for future beginners.

   

@ H L, I have registered a support case regarding this issue!!!

0 Likes
Reply
Anonymous
Not applicable
        🙂   
0 Likes
Reply