Posted on May 17, 2011 at 09:52Hi everyone,
The reference manual clearly states on page 253 that UART0 provides a full modem interface. I can clearly see the transmitted data on the oscilloscope on both RX (COM1 Pin 3) and TX (COM1 Pin 2) as well as in their corresponding GPIO pins 3.0 and 3.1. Other than that, I cannot get any signal on any other pin on COM1. Even pin 4 (Data Terminal Ready) which should be high when the UART is enabled is not enabled. As a matter of fact, except RX and TX pins the other pins on the COM1 are not even enabled, as I see on the scope only a ''50Hz noise signal'' similar to the one I get when the scope is powered on but not connected.
I would like to ask you guys if anyone has already tried to actually use the UART0 to communicate with a modem.
My application requires detecting the Ring and DCD signal level changes through interrupts and respond accordingly.
Here is my code, I have made sure that pins were assigned as described by the datasheet
//For Modem interface 2.0 to 2.3 default input functions
GPIO_DeInit(GPIO2);
GPIO_DeInit(GPIO3);
//UART0_Tx pin GPIO3.1 Alternate ouput 2 function
GPIO3->DDR |= 0x02;//output direction
SCU->GPIOOUT[3] |= 0x08; //Alternate ouput 2
//UART0_Rx pin GPIO3.0 Alternate inputs
GPIO3->DDR &= ~0x01;//input direction
SCU->GPIOIN[3] |= 0x01; //Alternate Input
//Pin 3.2 Alternate ouptut 2 UART0_DTR
GPIO3->DDR |= 0x04;//output direction
SCU->GPIOOUT[3] |= 0x30; //Alternate ouput 3
GPIO3->DR[0x3FC] = 0;
UART_InitStructure.UART_WordLength = UART_WordLength_8D;
UART_InitStructure.UART_StopBits = UART_StopBits_1;
UART_InitStructure.UART_Parity = UART_Parity_No ;
UART_InitStructure.UART_BaudRate = 9600;
UART_InitStructure.UART_HardwareFlowControl = ART_HardwareFlowControl_None;
UART_InitStructure.UART_Mode = UART_Mode_Tx_Rx;
UART_InitStructure.UART_FIFO = UART_FIFO_Disable;
//init UART0
UART_DeInit(UART0);
UART_Init(UART0, &UART_InitStructure);
// Enable UART0
UART_Cmd(UART0, ENABLE);
transmission and reception work, my application can communicate with the hyperterminal.
Here is what I observe:
Pin 3.3 (DTR) is high, while COM1 pin 4(DTR) is not enabled
Pins 2.0 (CTS) to 2.3 (Ring indicator) are all high even if a modem is not connected to COM1.
Do you have any explanation?
Any suggestion is much appreciated
Thanx
