Bug in switching baud rates in burst_ind branch?

Bhaskar11 niceguy108 at gmail.com
Fri Dec 28 06:16:04 UTC 2012


Hi Chris,

Thank you for the detailed explanation.

I am using a CP210x from Sysmocon. I understand that this has a
pre-programmed EEPROM and so does not require a driver. Yet, when I run
ccch_scan in burst_ind branch on Debian Linux, it fails both speeds.

The Tutorial does not mention need for installing a SiLabs driver, and all
attempts to install the Linux version of their driver fails. Can you
confirm if the driver is required?

But the same code in Windows works just fine as Windows permits selection
of any arbitrary speed. Of course I needed to install the SiLabs USB to
UART bridge driver for Windows to recognise the device in the first place.

B.


On Wed, Dec 26, 2012 at 2:05 AM, Christian Vogel <vogelchr at vogel.cx> wrote:

> Hi Bhaskar11,
>
>
> On Tue, 25 Dec 2012 15:35:03 +0100, Bhaskar11 <niceguy108 at gmail.com>
> wrote:
>
>> If the first attempt to switch to 406250 succeeds, the function exits and
>> never reaches the I_HAVE_A_CP210x code which would switch to a higher
>> speed!
>>
>
>  Is this a bug? Or is the lower speed good enough for burst_ind? In which
>> case why bother with the I_HAVE_A_CP210x option?
>>
>
> that logic is correct.
>
>
>  Or have I missed something obvious?
>>
>
> It's not about switching to a slighly higher baudrate of B460800 but
> rather to
> switch to the highest baudrate that can sensibly be used on the phone uart
> which
> is the non-standard 406250. Some USB/Serial converter chips allow to
> select almost
> any baudrate you want out of the box, but CP210x doesn't. If you have a
> CP210x you
> modify the eeprom in the serial adapter so that when Linux requests the
> "Standard"
> 460k, it actually uses the odd 406k.
>
> http://bb.osmocom.org/trac/**wiki/Hardware/CP210xTutorial<http://bb.osmocom.org/trac/wiki/Hardware/CP210xTutorial>
>
> In src/target/firmware/calypso/**uart.c there's the uint16_t divider[]
> table
> of baudrate dividers, and the two highest speeds supported by the calypso
> chipset are 406,250 or 812,500 bits per second.
>
> Silabs Application note AN205 explains the Silabs side of things.
>   http://www.silabs.com/Support%**20Documents/TechnicalDocs/**an205.pdf<http://www.silabs.com/Support%20Documents/TechnicalDocs/an205.pdf>
>
> Greetings,
>
>         Chris
>
>
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