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Question asked by Todd Wade on Dec 4, 2016
Latest reply on Dec 19, 2016 by jeremyzhou

I'm using a 48-pin LPC11U68, making use of USART0.  I'm having trouble getting *any* value for the CTS input. I'm using Port 0, pin 7 in the IOCON set up.  


I've tried enabling auto-cts, as well as setting up modem status interrupts, with the CTS change-of-state interrupt enabled too.  


To date I can see nothing that correlates to the CTS input.  When I read the CTS bit in the modem status register, it never reflects the current state of the CTS input, nor does the change-of-state ever move.


My setup:



Chip_UART0_SetModemControl(LPC_USART0, UART0_MCR_AUTO_CTS_EN);  <-- confirmed in MCR

Chip_UART0_IntEnable(LPC_USART0, (UART0_IER_RBRINT | UART0_IER_RLSINT | UART0_IER_MSINT | UART0_IER_CTSINT)); <-- Confirmed in register

In my ISR, I never see a change of CTS state, even though the input definitely has a changing input.

Auto-CTS is not working, in that TX continues regardless of the CTS input from the receiving device.

I saw another post about this very issue, and no one responded.  Is this a known problem with this port, or is there some secret sequence to configure it for correct operation?