Difference between revisions of "OneWire GPIO bus Master"
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| − | Informations and HOWTOs for | + | Informations and HOWTOs for Armadeus OneWire support. |
| − | Author: JanosA | + | Author: [[User:JanosA]] |
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| + | == Supported boards and software versions == | ||
| + | * Use the latest Armadeus GIT/SF repository or the latest stable release. | ||
| + | * Currently only the [[APF28Dev]] board is upported, but it's easy to add support to another boards. (Check linux-2.6.35.3/arch/arm/mach-mx28/apf28dev.c file) | ||
== Software installation == | == Software installation == | ||
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</pre> | </pre> | ||
* Reflash your Linux kernel | * Reflash your Linux kernel | ||
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== Hardware Notes == | == Hardware Notes == | ||
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* GND is pin 39 on J9 | * GND is pin 39 on J9 | ||
* Add an 1.2k pullup resistor between Vcc and DQ | * Add an 1.2k pullup resistor between Vcc and DQ | ||
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== How it works == | == How it works == | ||
Revision as of 09:42, 7 January 2014
Informations and HOWTOs for Armadeus OneWire support.
Author: User:JanosA
Contents
Supported boards and software versions
- Use the latest Armadeus GIT/SF repository or the latest stable release.
- Currently only the APF28Dev board is upported, but it's easy to add support to another boards. (Check linux-2.6.35.3/arch/arm/mach-mx28/apf28dev.c file)
Software installation
- Recompile your Linux kernel with OneWire GPIO bus master (and some slave device) support.
$ make linux-menuconfig
Device Drivers --->
<*> Dallas's 1-wire support --->
1-wire Bus Masters --->
<*> GPIO 1-wire busmaster
1-wire Slaves --->
<*> Thermal family implementation
$ make
- Reflash your Linux kernel
Hardware Notes
- Connect the OneWire slave directly to the APF28_DEV board J9 connector:
* Vcc 3.3V is pin 1 on J9 connector * DQ is pin 31 on J9 (LCD_D18 / GPIO 1_18) * GND is pin 39 on J9
- Add an 1.2k pullup resistor between Vcc and DQ
How it works
The OneWire bus master driver every 10 seconds scan the bus for new slave devices.
Each detected OneWire slave device have a sub-directory with it's unique ID in "/sys/devices/w1 bus master".
The sub-directory format is <2 digit family ID>-<12 digit unique ID>.
# ls -la /sys/devices/w1\ bus\ master/ total 0 drwxr-xr-x 4 root root 0 Jan 1 01:06 . drwxr-xr-x 6 root root 0 Jan 1 01:05 .. drwxr-xr-x 3 root root 0 Jan 1 01:06 28-000001e68904 lrwxrwxrwx 1 root root 0 Jan 1 01:07 driver -> ../../bus/w1/drivers/w1_master_driver drwxr-xr-x 2 root root 0 Jan 1 01:07 power lrwxrwxrwx 1 root root 0 Jan 1 01:07 subsystem -> ../../bus/w1 -rw-r--r-- 1 root root 4096 Jan 1 01:07 uevent -rw-rw-rw- 1 root root 4096 Jan 1 01:07 w1_master_add -r--r--r-- 1 root root 4096 Jan 1 01:07 w1_master_attempts -r--r--r-- 1 root root 4096 Jan 1 01:07 w1_master_max_slave_count -r--r--r-- 1 root root 4096 Jan 1 01:07 w1_master_name -r--r--r-- 1 root root 4096 Jan 1 01:07 w1_master_pointer -rw-rw-rw- 1 root root 4096 Jan 1 01:07 w1_master_pullup -rw-rw-rw- 1 root root 4096 Jan 1 01:07 w1_master_remove -rw-rw-rw- 1 root root 4096 Jan 1 01:07 w1_master_search -r--r--r-- 1 root root 4096 Jan 1 01:07 w1_master_slave_count -r--r--r-- 1 root root 4096 Jan 1 01:07 w1_master_slaves -r--r--r-- 1 root root 4096 Jan 1 01:07 w1_master_timeout
You can list the detected slaves from this files:
# cat /sys/devices/w1\ bus\ master/w1_master_slave_count 1 # cat /sys/devices/w1\ bus\ master/w1_master_slaves 28-000001e68904
Let's read the temperature: (The 28-xxx family is a DS18B20 temperature sensor in this example.)
# cat /sys/devices/w1\ bus\ master/28-000001e68904/w1_slave dd 01 4b 46 7f ff 03 10 1e : crc=1e YES dd 01 4b 46 7f ff 03 10 1e t=29812
The t=29812 means, the temperature is: 29.812°C
