Hi,

I have a problem with AT91SAM7X USART1 in 'Modem mode'.
AT91 is connected to a GSM modem and all the serial modem signals are connected to the related modem pins.
When I use hardware-handshake mode of the UART in AT91, everything is OK and modem works fine. If I change the mode to 'Modem mode', AT91 UART cannot receive anything when DCD goes low.
When modem connects to the server, it drags its DCD pin to low level in order to show that connection has been made. From this point on, nothing from the modem reaches AT91. I have used an oscilloscope and have seen that data reaches to the modem and being sent to AT91. But AT91 buffer does not get any thing. Funny thing is that transmitting to the server works and AT91 can send the data through the modem.

Any idea?

Thinks in advance,
Iman

Be sure the modem has a FIXED DTE speed and not setup to switch baud rates on you for the connection speed.
Look at the 'CONNECT' message and the configuration.

-James

Thanks James.

But the DTE speed is fixed and as I said ARM sends the data to the server thru the modem (shows that it is not a baud rate problem). But cannot receive anything.

Had the same problem, i just didn't connect DCD. No fix as far as Im aware of.

Hi!
I think the USART Errata in the datasheet can help you: in modem mode "DCD is Active High instead of Low"
ovicod

suppose to have the same ptoblem:
have a SAM7X256 and GSM modem so need chage the baudrate on fly from 28800 to 115200
after chaging baudrate I see data on oscillograph but non data in buffer!
UART initialization procedure:
void USART_init(unsigned int baudrate) {
AT91C_BASE_US0->US_CR = AT91C_US_RSTRX |
AT91C_US_RSTTX |
AT91C_US_RXDIS |
AT91C_US_TXDIS;

AT91F_PIO_CfgPeriph(
AT91C_BASE_PIOA, AT91C_PA0_RXD0 | AT91C_PA1_TXD0,
0 );

AT91F_PMC_EnablePeriphClock(AT91C_BASE_PMC, 1<<AT91C_ID_US0);

AT91C_BASE_US0->US_IER = AT91C_US_ENDRX | AT91C_US_RXRDY;

AT91F_US_Configure (AT91C_BASE_US0,
MCK,
AT91C_US_ASYNC_MODE | AT91C_US_NBSTOP_2_BIT,
baudrate,
0);

AT91C_BASE_US0->US_CR = AT91C_US_RXEN | AT91C_US_TXEN;

AT91F_AIC_ConfigureIt(AT91C_BASE_AIC,
AT91C_ID_US0,
INTERRUPT_LEVEL_7,
AT91C_AIC_SRCTYPE_INT_HIGH_LEVEL,
Usart0_c_irq_handler);

AT91C_BASE_US0->US_RPR = (unsigned int)&buff_rx;
AT91C_BASE_US0->US_RCR = 256;
AT91C_BASE_US0->US_TCR = 0;

AT91C_BASE_US0->US_RTOR = 10000;

AT91F_PDC_Open(AT91C_BASE_PDC_US0);
AT91F_AIC_EnableIt(AT91C_BASE_AIC, AT91C_ID_US0);
}

so simply trying to call above procedure with another baudrate speed
. . . // code ARM - Modem on 28800 baudrate
AT91C_BASE_US0->US_THR = 0x21;
sleep(100);
AT91F_US_Put(AT91C_BASE_US0, baseAddress, 4);
sleep(100);

USART_init(115200); // trying change baudrate

sleep(100);
AT91C_BASE_US0->US_THR = 0x21;
sleep(100);
AT91C_BASE_US0->US_THR = 0x00; // after this message we should receive 160 byte from modem So they come (I see it on oscillograph) but in buff_rx there are nothing!
any ideas?

Can a wireless cable modem interfere with satellite tv? I just had installed a wireless cable modem and it sits within 1 foot of my satellite receiver box. The receiver has since been constantly losing signal, while my other tv in another room with it's own receiver has been doing fine. I have tried to power down both the modem and the satellite receiver with no luck. Any solutions?
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