CY8CKIT-059 / Kitprog / 3.3V Operation Questions

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
KaAs_973901
Level 2
Level 2

Although I've seen a few variations of this questions, I would like to verify some additional points prior to modifying the prototyping board. Section 4.2.3 details the options around powering the device. 

   

When powering from an external regulated supply connected to VDD: 

   
    

"KitProg measures the target voltage and adjusts the logic levels on the programming pins accordingly."

   
   

Three questions from this: 

   

1) Which pin does the KitProg sample to measure the target voltage?

   

2) For the UART_TX, UART_RX, I2C_SDA, and I2C_SCL signals that are connected between the target and KitProg, do those logic levels also become adjusted based on the target voltage? Or, would they need to be broken apart and run through level shifters. 

   

I would like to continue using the USB-UART functionality even when the target is 3.3V powered. 

   

3) I am unable to tell for certain if a 3.3V powered target will still have 5V tolerant pins. 

   

Thanks, 
Karl 

0 Likes
3 Replies
Anonymous
Not applicable

Hi Karl

   

Kitprog is using SIO Pins to do the programming communication.

   

This pins have a reference voltage input which is used to adjust the levels.
Saying that the other I/Os you mentioned are not adjusted and run with 5V.
If you want to run the PSoC with 3.3V you will need to snap of the KitProg and connect the programming interface of it seperatly.

   

I have prepared some time ago a video addressing the use of KitProg with 3.3V Targets:

   

https://www.youtube.com/watch?v=0UMXdJHwh_U&sns=em

   

In case you are running the PSoC with 3.3V the I/O pins are not 5V tolerant.

   

All the Best
Frank

0 Likes

Great information, I will include level shifters for the UART and I2C. 

   

Thank you for taking the time to make that video!

   

Karl

0 Likes
AnkitaS_51
Employee
Employee
100 likes received 50 likes received 25 likes received


SIO supports programmable output level and programmable input threshold. The logic is to sense the voltage level using ADC and adjust the SIO pin output. We have also implemented similar functionality for UART and I2C pins internally. Thus there is no need of level shifter at these lines. Please let us know if you face any discrepancies. We tried to recreate the same and observed 3.3 V at SDA lines without level shifter.

0 Likes