CCS/TMS320C5535: GPIO reading input issues

Jonathan Wagner

Part Number: TMS320C5535

Tool/software: Code Composer Studio

Hello,

I am currently using the TMS320C5535 eZdsp USB kit for a project, and I am attempting to read in values using the CSL functions for this processor. However, I never get a logical high value. I have tried using an input of 3.3V from VCC_3V3 pins on the eZdsp kit itself, as well as from an external power supply, to no avail. My question is, is this a problem in my code somewhere? Or is this an issue with how I am trying to send a signal into the pin? For my code, I am calling functions from the file ezdsp5535_gpio.c in my main, and this file calls functions from the CSL, specifically from csl_gpio.c. Outputting values with the GPIO pins works correctly, which leads me to believe it may be a problem with my sending of the signal and not the code itself.

Thank you for any help you can offer.

over 6 years ago

0 Cvetolin Shulev-XID over 6 years ago

TI__Guru 65405 points

Hi Jonathan,

As CSL GPIO demo works properly you should focus on investigating sending of the signal.

BR
Tsvetolin Shulev

0 Jonathan Wagner over 6 years ago in reply to Cvetolin Shulev-XID

Prodigy 80 points

Okay, thank you for narrowing it down. I had a few more questions then regarding reading the signal. 3.3V should be an acceptable input to register as a logical high value right? And it is acceptable to read in an analog signal using GPIO pins?

0 Cvetolin Shulev-XID over 6 years ago in reply to Jonathan Wagner

TI__Guru 65405 points

Datasheet Table 3-2 give information about Supported I/O voltages 1.8 V, 2.5 V, 2.75 V, 3.3 V. Yes, 3.3 V is acceptable high input level.

Also you can find voltage range acceptable for High-level (VIH) and low-level (VIL) input voltage in section 5.2 Recommended Operating Conditions.

It is not recommended to input analog signals to GPIO if you are not ensure that levels between Vih and Vil will not be sent. If you guarantee that the level of analog signals will be below Vil and above Vhl should be acceptable.

Tsvetolin Shulev

0 Jonathan Wagner over 5 years ago in reply to Cvetolin Shulev-XID

Prodigy 80 points

Thank you very much for your help. I was able to successfully read in a signal to the GPIO pin today. It ended up being a connection issue with the PCB connected to our edge connector. After re-soldering the connections it worked the first time I tried.

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CCS/TMS320C5535: GPIO reading input issues