1 ====================
2 Kernel driver ds2490
3 ====================
4
5 Supported chips:
6
7 * Maxim DS2490 based
8
9 Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
10
11
12 Description
13 -----------
14
15 The Maxim/Dallas Semiconductor DS2490 is a chi
16 which allows to build USB <-> W1 bridges.
17
18 DS9490(R) is a USB <-> W1 bus master device
19 which has 0x81 family ID integrated chip and D
20 low-level operational chip.
21
22 Notes and limitations.
23
24 - The weak pullup current is a minimum of 0.9m
25 - The 5V strong pullup is supported with a min
26 maximum of 30.4 mA. (From DS2490.pdf)
27 - The hardware will detect when devices are at
28 next bus (reset?) operation, however only a
29 the core w1 code doesn't make use of the inf
30 one device tends to give multiple new device
31 - The number of USB bus transactions could be
32 was added to the API. The name is just a su
33 a write buffer and a read buffer (along with
34 The ds2490 block I/O command supports reset,
35 buffer, and strong pullup all in one command
36 1 reset bus, 2 write the match rom command a
37 write and read data. The write buffer needs
38 command and slave rom id prepended to the fr
39 write buffer, both of which are known to the
40 - The hardware supports normal, flexible, and
41 communication speeds, but only the normal is
42 - The registered w1_bus_master functions don't
43 conditions. If a bus search is in progress
44 removed it can produce a good amount of erro
45 search finishes.
46 - The hardware supports detecting some error c
47 short, alarming presence on reset, and no pr
48 driver doesn't query those values.
49 - The ds2490 specification doesn't cover short
50 detail, but my observation is if fewer bytes
51 available, the bulk read will return an erro
52 clear the entire bulk in buffer. It would b
53 maximum buffer size to not run into this err
54 bytes in the buffer is a logic error in the
55 match reads and writes as well as data sizes
56 writes are serialized and the status verifie
57 (and data is available) before the read is e
58 not happen.
59 - Running x86_64 2.6.24 UHCI under qemu 0.9.0
60 with a OHCI controller, ds2490 running in th
61 normally the first time the module was loade
62 the ds2490 hardware, but if the module was u
63 most of the time one of the bulk out or in,
64 would fail. qemu sets a 50ms timeout and th
65 even when the status shows data available.
66 show a successful completion, but the ds2490
67 show 0 bytes written. Detaching qemu from t
68 reattaching would clear the problem. usbmon
69 host did not explain the problem. My guess
70 or the host OS and more likely the host OS.
71
72 03-06-2008 David Fries <David@Fries.net>
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