From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <13426df10802040843l76932e5at1413a975f3f38bf7@mail.gmail.com> Date: Mon, 4 Feb 2008 08:43:13 -0800 From: "ron minnich" To: "Fans of the OS Plan 9 from Bell Labs" <9fans@cse.psu.edu> Subject: Re: [9fans] 9pcf debugging In-Reply-To: <45219fb00802040818v440cfee9q71e6ac585f07fb8e@mail.gmail.com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_10329_354900.1202143393605" References: <45219fb00802040818v440cfee9q71e6ac585f07fb8e@mail.gmail.com> Topicbox-Message-UUID: 44ce39aa-ead3-11e9-9d60-3106f5b1d025 ------=_Part_10329_354900.1202143393605 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline We had this problem too on LinuxBIOS, and it's a real problem when you've just powered on and have no memory or stack. But some vendors are claiming they have dropped serial to save money, since we have "the Universal Serial Bus for serial I/O". Fortunately, the universal serial bus guys finally figured out, TEN YEARS LATE, that they had not actually provided a workable serial bus mechanism for debugging. Yup, it finally hit them that they somehow forgot to make up a simple serial output, and that running those serial dongles was a bit more than most bioses could get, esp. when there is no stack available. It hit them just about the time somebody said, "I want to remove the serial port, how do I debug?" Ah, USB. 24+ chapters and not a single good idea :-) [ok, maybe one: powered cables are nice] There is a fix. Well, two fixes. First off, in light of USB's utter uselessness for debugging, most vendors still put COMA on their boards -- they just don't bring it out to a connector. This is true on almost every board I have, including a "consumer" board I have here which is advertised not to have serial! So open the box and look for COMA. It's usually a 10-pin header, two rows of 5 pins, .1 inch centers, with (if you're lucky) a giant COMA label next to it.Sometimes they clip one pin so it is oriented. Option two is really cute, and could only have been a USB invention. Basically, since there is no easy way to debug the Universal Serial Bus, they created this kludge called the Debug port. Here's a talk on it: http://www.usb.org/developers/presentations/pres0602/john_keys.pdf note that when a port is used for usb debug, it's disabled for USB. Cute, huh? You need to get a debug port dongle, which is so simple it only needs two small embedded controllers to work. Here is one: http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=12083 it's only $83, which is more than most motherboards, but hey ... So, look for the COMA connector first. Last resort: usb debug port. thanks ron ------=_Part_10329_354900.1202143393605 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline We had this problem too on LinuxBIOS, and it's a real problem when you've just powered on and have no memory or stack. But some vendors are claiming they have dropped serial to save money, since we have "the Universal Serial Bus for serial I/O".

Fortunately, the universal serial bus guys finally figured out, TEN YEARS LATE, that they had not actually provided  a workable serial bus mechanism for debugging. Yup, it finally hit them that they somehow forgot to make up a simple serial output, and that running those serial dongles was a bit more than most bioses could get, esp. when there is no stack available. It hit them just about the time somebody said, "I want to remove the serial port, how do I debug?"

Ah, USB. 24+ chapters and not a single good idea :-)
[ok, maybe one: powered cables are nice]

There is a fix. Well, two fixes. First off, in light of USB's utter uselessness for debugging, most vendors still put COMA on their boards -- they just don't bring it out to a connector. This is true on almost every board I have, including a "consumer" board I have here which is advertised not to have serial!

So open the box and look for COMA. It's usually a 10-pin header, two rows of 5 pins, .1 inch centers, with (if you're lucky) a giant COMA label next to it.Sometimes they clip one pin so it is oriented.

Option two is really cute, and could only have been a USB invention. Basically, since there is no easy way to debug the Universal Serial Bus, they created this kludge called the Debug port.
Here's a talk on it:http://www.usb.org/developers/presentations/pres0602/john_keys.pdf

note that when a port is used for usb debug, it's disabled for USB. Cute, huh?

You need to get a debug port dongle, which is so simple it only needs two small embedded controllers to work. Here is one: http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=12083

it's only $83, which is more than most motherboards, but hey ...

So, look for the COMA connector first. Last resort: usb debug port.

thanks

ron
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