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AM335x Booting configuration pins and UART pins - MUX conflict

Vladimir Zlatev
Prodigy 210 points

Hello

In the project that I developed, using all UART ports, [UART 0...5]. and another Peripheral Interfaces.

I have to use pins: 

UART5_TXD_MUX2
UART5_RXD_MUX2

and

UART3_CTSN_MUX1
UART3_RTSN_MUX1

But, in the same pins are located SYSBOOT Configuration Pins also known as: LCD DATA 0 ....15.  

The situation by configuring the AM335x pins is the following:  I do not have much choice on the definition of UART5 and UART3 pins 

I must to use this pins.

My questions is:

Can I use UART5 and UART3  without problems?
After initialization, the sysboot pull-up or pull-down resistors it will hinder the work of UART communication?

Тhanks in advance.


  • 0
    TI__Guru**** 393215 points
    Hi Vladimir,
     
    Yes, you can use these pins for UART without problem. If you use 100kOhm pullup resistors and 10kOhm pulldown resistors for SYSBOOT config, they shouldn't hinder the UART I/O in any way.
  • 0 in reply to Biser Gatchev-XID
    TI__Guru 62825 points

    Keep in mind these terminals power-up in GPIO mode with outputs disabled.  So the logic state of these terminals will be defined by the external pull-up or pull-down resistors.  These pull-up or pull-down logic levels may cause to UART transceivers to drive an unexpected level to attached devices.

    You may need to disable the UART transceiver outputs until the respective UART and pin multiplexing registers are configured if this causes a system level issue for your product.

    Regards,
    Paul