[sane-devel] [Update] Canon 4200F USB chip location

[LUH LAH]

Thanks for replying,

Before I want to even consider doing all that, I need a suspicion of
mine answered. I think that the Canon 4200F is nearly interchangeable
with the 4400F, and can use its already written driver.

Can you guide me on how I would use the driver for this scanner?

Thanks,

-[K] IMSOASIAN

On 11/22/21, Ralph Little <skelband at gmail.com> wrote:
> Hi,
>
> On 2021-11-20 2:56 p.m., LUH LAH wrote:
>> Hello there!
>>
>> It's been over a month since I last inquired about this, but I have an
>> update and need some more guidance.
>>
>> I installed Windows 7 on another computer I had and captured packets
>> from when I pressed the 'Scan' button in the CanoScan tool.
>>
>> Now that I've got the packets captured in a .pcapng file
>> (https://drive.google.com/file/d/1E0zErjd0PB3Ggmeop6iI43Gi0SCZ8K9m/view?usp=sharing),
>> how do I analyze the packets and figure out the USB chip model?
>>
>> Thanks,
>>
>> -[K] IMSOASIAN
>>
>>
>> (This is a continuation of a previous thread. Said thread can be found
>> here:
>> https://alioth-lists.debian.net/pipermail/sane-devel/2021-October/thread.html
>> [Look for a thread mentioning a Canon 4200F by LUH LAH])
>>
> This is a difficult question to answer simply.
>
> The first step would be to determine if the protocol is supported by an
> existing backend.
> Unfortunately, we do not have much documentation about the protocols
> that are currently supported with which to compare.
> We usually get hints based on the chippery found inside. For this
> machine, it sounds like it is just a standard set of components that
> doesn't give us much of a clue.
>
> It might be that since this is a Canon scanner, then it might borrow
> some heritage from one of their other models from the time that are not
> using one of the standard scanner all-in-one chips.
>
> Failing that, if you want to start to look at writing a backend for this
> scanner from scratch, you need to look in the USB conversation for the
> various parts of the scanning process and the conversation would
> typically follow the following sequence:
>
> 1) Reset: some sequences to get the scanner into a known state. It might
> start with a sequence intended to get the scanner's attention.
> 2) Setting of parameters followed by calibration operations. Generally
> includes scans of a black and white area under the case to get the
> proper balance for each scan head pixel, since there is typically
> variation between them so correction is required. If the scanner is
> doing this, the you will notice the scan head make some short passes
> before the actual scan.
> 3) Scan proper: setting up of motor acceleration table, setting
> parameters for the scan head etc and the proceeding with the scan
> itself. This phase will be *very* obvious looking at the trace as there
> will be large blocks of data being transferred to the PC.
> 4) Instructions to bring the scanning head back to the parking position.
>
> I would start with trying to split the trace into those rough sections.
> One initial thing you can try is to extract the bytes from the trace
> during the scanning phase, assemble them into a file and try to view
> them as a graphic to figure out the format.
> Dropping the bytes into a PNM format file is handy and then you can
> experiment with the header parameters to get an image that looks correct.
>
> Cheers,
> Ralph
>