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Dockstar, I2C bus
The Marvell 88F6281 SoC (System On Chip) has an I2C bus connection, not brought out to a plug, but the pullup resistors are there.
The Linux kernel needs to have an I2C driver enabled for to use, please see at the links.
I2C bus, Hardware
The data and clock connection points can be found (see pictures):
- TW_SDA MPP[8] R268 4K7 pullup, board upper side at R23
- TW_SCK MPP[9] R269 4K7 pullup, board lower side beside C64
I soldered a 4 pin (spacing 2.54 mm) header to the board, please see the picture. The signals are:
+3.3 V for I2C devices with low current only
- SCK (clock, about 140 KHz)
- SDA (data)
- GND
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For wiring I used thin wire-wrap wire. It works best to give a little flux to the soldering points of the board.
The housing must be cut out, that you can plug a connector, if the housing is closed. Also part of the shield on the inside of the housing must be bend up, to avoid any electric contact to the pins.
I2C bus, Software
shyd was so friendly and compiled the Linux kernel version 3.9.5 for the Dockstar, including I2C support. You can also download there:
Linux kernel config file
Linux kernel header file in order to compile yourself
Linux kernel patch file, against the official sources
For installation details please have also a look at Dockstar Debian.
Check the I2C interface with an I2C slave connected to the bus:
$ sudo apt-get install i2ctools
# look for the device
$ ls -ls /dev/i2*
0 crw-rw---T 1 root i2c 89, 0 Jan 1 1970 /dev/i2c-0
# look for I2C slaves
$ sudo i2cdetect -y 0
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- 04 -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- 64 -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
# The address 04 is an ATtiny85 listening to I2C
Links
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-- RudolfReuter 2013-12-23 17:21:17
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