Moe Trin
Guest
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 Posted:
Fri Nov 12, 2004 7:50 am Post subject:
Re: PCMCIA modem fails when sending AT commands without dela |
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In article <6966c3f8.0411110359.5d235a78@posting.google.com>, samraj wrote:
| Quote: | We have tried to debug the Sierra wireless modem AirCard 750(PCMCIA)
interfaced to our PowerPC 8270 based target through TI PCI1520 (PCI to
PCMCIA controller).
We used the "Linux Configuration for AirCardŽ 55x and 7xx" Application
note 2170005 dated June 3 2002
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You might want to try over in comp.os.linux.portable and
comp.os.linux.powerpc.
| Quote: | The Sierra wireless card emulates a 16550 UART serial port interface.
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16550 or 16550_A_ ??? There is a difference. The 16550 without the
A effectively has a one byte buffer, while the 16550A (and later) had
a working 16 character buffer. 9600 BPS (Bits, not Bytes) was about the
limit in the earlier chips, while the A model could handle 115200 BPS.
| Quote: | 1. The above operations were successful when the AT commands were sent
with a delay (approximately 1 sec) between each character written to
the virtual serial port transmit register.
The modem responds with "OK" or relevant success message.
2. These operations fail when the delays are removed. The modem
responds with error messages like "NO CARRIER" and "+CMS ERROR: 513".
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I'm not a PPC person, and I don't use PCMCIA. Normally, these kinds
of errors indicate a flow control or interrupt problem.
| Quote: | We thought that the errors could be due to baud rate mismatch. Hence
we have tried with baudrates : 19200 and 38400 but the test did not
succeed.
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No, and if it were, I'd be going in the opposite direction (slower).
| Quote: | Why don't the AT commands pass without inserting delays after each
character sent?.
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How long are the commands? Could you be overflowing the FIFO buffer?
What connect speed are the modems negotiating with each other? That's
why I more suspect flow control problems. You'd also want to mention
how you are sending the commands to the modem - minicom, seyon, cu, or
something?
Old guy |
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