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Disabling OMAPL138 UART CTS?

John Wilkes
Expert 1315 points

Hello,

Is there any way of disabling the CTS input in a L138 UART module? I am not using the autoflow feature and do not want to use the CTS/RTS handshaking. However, the UART will not transmit if this line is in the wrong state. I can force the pin on the device and it works fine, but the pin in multiplexed with another I want to use (UART1 CTS is muxed with a McASP clock). Does this mean I cannot use UART1 and McASP at the same time?

Cheers,

John.

  • 0
    Guru 26430 points

    Some speculation. I've only had to deal with 2 wire serial in the L137. I think that you should able to pinmux only Tx and Rx. Leave the nRTS and nCTS lines unmuxed. They should have internal pullups to fool any drivers that might use them. Ideally, the drivers should be configured not to use them. On Linux, the 8250 driver is very complicated and looks to be hard to configure for no HW flow control. In the Linux DVSDK, there is a kernel config that controls the pinmux of flow control pins, CONFIG_DAVINCI_UART1_AFE. No idea about BIOS and PSP. From your other thread, I am guessing you want to McASP on the ARM/Linux side and UART1 on the DSP side.

  • 0 in reply to Norman Wong
    TI__Genius 14405 points

    You should be able to accomplish this by making sure the AFE bit of MCR register is cleared to zero.

    regards,

    Paul

  • 0 in reply to Paul.Yin
    Expert 1315 points

    Oops!

    Sorry chaps but the CTS line turned out to be a red herring. There was a bug on my board that meant that the TX and RX signals where not always getting through to the L138. With this fixed the UART works fine regardless of what the CTS is MUXed to. Sorry to have wasted your time with this but thanks for your replies anyway.

    Cheers,

    John.