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/Documentation/misc-devices/c2port.txt

https://gitlab.com/vibisreenivasan/UML
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 1			C2 port support
 2			---------------
 3
 4(C) Copyright 2007 Rodolfo Giometti <giometti@enneenne.com>
 5
 6This program is free software; you can redistribute it and/or modify
 7it under the terms of the GNU General Public License as published by
 8the Free Software Foundation; either version 2 of the License, or
 9(at your option) any later version.
10
11This program is distributed in the hope that it will be useful,
12but WITHOUT ANY WARRANTY; without even the implied warranty of
13MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14GNU General Public License for more details.
15
16
17
18Overview
19--------
20
21This driver implements the support for Linux of Silicon Labs (Silabs)
22C2 Interface used for in-system programming of micro controllers.
23
24By using this driver you can reprogram the in-system flash without EC2
25or EC3 debug adapter. This solution is also useful in those systems
26where the micro controller is connected via special GPIOs pins.
27
28References
29----------
30
31The C2 Interface main references are at (http://www.silabs.com)
32Silicon Laboratories site], see:
33
34- AN127: FLASH Programming via the C2 Interface at
35http://www.silabs.com/Support Documents/TechnicalDocs/an127.pdf 
36
37- C2 Specification at
38http://www.silabs.com/pages/DownloadDoc.aspx?FILEURL=Support%20Documents/TechnicalDocs/an127.pdf&src=SearchResults
39
40however it implements a two wire serial communication protocol (bit
41banging) designed to enable in-system programming, debugging, and
42boundary-scan testing on low pin-count Silicon Labs devices. Currently
43this code supports only flash programming but extensions are easy to
44add.
45
46Using the driver
47----------------
48
49Once the driver is loaded you can use sysfs support to get C2port's
50info or read/write in-system flash.
51
52# ls /sys/class/c2port/c2port0/
53access            flash_block_size  flash_erase       rev_id
54dev_id            flash_blocks_num  flash_size        subsystem/
55flash_access      flash_data        reset             uevent
56
57Initially the C2port access is disabled since you hardware may have
58such lines multiplexed with other devices so, to get access to the
59C2port, you need the command:
60
61# echo 1 > /sys/class/c2port/c2port0/access
62
63after that you should read the device ID and revision ID of the
64connected micro controller:
65
66# cat /sys/class/c2port/c2port0/dev_id
678
68# cat /sys/class/c2port/c2port0/rev_id
691
70
71However, for security reasons, the in-system flash access in not
72enabled yet, to do so you need the command:
73
74# echo 1 > /sys/class/c2port/c2port0/flash_access
75
76After that you can read the whole flash:
77
78# cat /sys/class/c2port/c2port0/flash_data > image
79
80erase it:
81
82# echo 1 > /sys/class/c2port/c2port0/flash_erase
83
84and write it:
85
86# cat image > /sys/class/c2port/c2port0/flash_data
87
88after writing you have to reset the device to execute the new code:
89
90# echo 1 > /sys/class/c2port/c2port0/reset