UART demo Project with UART1

[jeremyanderson]

I'm using the FRDM-K66F board and running the freertos_uart demo project.  It works well enough through UART0, but this is carried through the USB debug connection and I need to look at the signal on the wire.  I changed the demo project to use UART1 instead by the following steps:

1. Connect pins A9 and A11 to UART1 TX and RX by updating pin_mux.c

2. Change the DEMO_UART* symbols to refer to UART1 instead of UART0

3. Connect J1 pin 4 to pin 2 on the DE9 serial connector.

4. Connect J1 pin 2 to pin 3 on the serial connector.

5. Connect J3 pin 12 to pin 5 on the serial connector.

I can see that pin 2 on the serial connector is where I want to transmit because my script that watches the port picks up the noise when I disconnect and reconnect that wire.  I've stepped through the code and see that the UART_WriteNonBlocking function is entered and eight characters are written to the D register on each pass until the last one which only has seven.  So it seems we've done the right thing, but nothing is seen on the other end.  I can see also that the UART1 driver IRQ handler is invoked..  This really looks like a pin issue.  When I get to the receive part of the demo, the software always ends up terminating on a timeout on the event group wait.

Any experience with this out there?

[jeremyanderson]

hOne more note on this.  I found that the data I was getting on the console side was inverted when using UART1.  I set the TXINV bit in register C3 and everything looks good from the transmit standpoint.  I still don't get anything back on the receive pin (J1-2).  Why would UART1 present mark for space with respect to UART0?

[jeremyanderson]

OK, thanks Daniel.  I see what is going on now.  The TTL levels at the pins present inverted values when connected to the RS-232 lines on my docking station serial port.  This turns out to have been a matter of my own ignorance, now remedied.  Thanks for the help!

[danielchen · Accepted solution]

Hi Jeremy Anderson:

I did a quick test according to your modifications. I tested with my uart-to-usb , and it can work on my side.

My modifications :

1. pin_mux.c

void BOARD_InitPins(void) {
  CLOCK_EnableClock(kCLOCK_PortC);                           /* Port B Clock Gate Control: Clock enabled */

  PORT_SetPinMux(PORTC, PIN3_IDX, kPORT_MuxAlt3);           /* PORTB16 (pin E10) is configured as UART0_RX */
  PORT_SetPinMux(PORTC, PIN4_IDX, kPORT_MuxAlt3);           /* PORTB17 (pin E9) is configured as UART0_TX */  
 
}

 2 freertos_uart.c

#define DEMO_UART UART1
#define DEMO_UART_CLKSRC SYS_CLK
#define DEMO_UART_CLK_FREQ CLOCK_GetFreq(SYS_CLK)
#define DEMO_UART_RX_TX_IRQn UART1_RX_TX_IRQn

Have a great day,
Daniel

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[jeremyanderson]

Just one more note here, I see in your example the comments indicate UART0 (cut and pasted I'm sure) but these actually connect PORTC3 (pin A11) and PORTC4 (pin A9) to UART1.

[jeremyanderson]

OK, partial answer.  My eyes are going, but sending the same message over the UART0 link results in a coherent transmission, whereas UART1 ends up sending an extra byte and none of it makes any sense.  It looks like noise might be an issue since this is a kludged up experiment.