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interfaces:1wire [2015/10/22 20:52]
darron 		interfaces:1wire [2016/01/20 10:21] (current)
darron [KEYES DS18B20 module]
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 +==== 1wire bus ====
 +<wrap right>
 +{{:interfaces:1wire.jpg?200}}
 +\\ \\
 +{{:interfaces:1wire-2.jpg?200}}
 +\\ \\
 +{{:interfaces:keyes.jpg?200}}
 +</wrap>
 +
 +The 1wire bus supports various low speed digital devices and is supported in Linux on the Raspberry Pi.
 +
 +=== Raspberry Pi ===
 +
 +Edit boot/config.txt to assign gpio4 for 1wire.
 +<code>
 +dtoverlay=w1-gpio,gpiopin=4
 +</code>
 +
 +Reboot and after load driver.
 +<code>
 +modprobe w1_gpio
 +</code>
 +
 +These are the GPIO header pin assignments for the 1 wire bus.
 +
 +^Pin ^Name  ^Function |
 +| 1  | 3V3 | POWER|
 +| 6  | GND| GROUND |
 +| 7  | GPIO4 | DATA|
 +
 +The relevant pins on the Pi header are as follows.
 +<code>
 +                +---P1---+
 +3V3             01      02 5V
 +GPIO0/GPIO2     03 A/A+ 04 5V
 +GPIO1/GPIO3     05 B/B+ 06 GND
 +GPIO4           07 2    08 GPIO14/TX
 +                ..      ..
 +</code>
 +
 +NB. The 1 wire data line must pulled high via 4K7 to 3V3 power.
 +
 +
 +=== DS18B20 Thermometer ===
 +<code>
 ++-------+
 +| 1 2 3 |
 ++-------+
 +  | | |
 +  | | |
 +  
 +1 GROUND
 +2 DATA
 +3 POWER
 +</code>
 +
 +<code>
 +modprobe w1_therm
 +cat /sys/bus/w1/devices/28-041460bdd6ff/w1_slave 
 +8f 01 55 00 7f ff 0c 10 a0 : crc=a0 YES
 +8f 01 55 00 7f ff 0c 10 a0 t=24937
 +</code>
 +
 +=== KEYES KY-001 DS18B20 module ===
 +
 +This module re-orders the pins so beware.
 +
 +<code>
 ++-------+
 +|DS18B20|
 +|       |
 ++-G R Y-+
 +  | | |
 +  
 +G GROUND
 +R POWER
 +Y DATA
 +</code>
 +
 +DATA is pulled up via a 4K7 resistor and an LED. The LED will flash
 +during communication with the chip.
 +=== DS2431 EEPROM ===
 +<code>
 ++-------+
 +| 1 2 3 |
 ++-------+
 +  | | |
 +  | | |
 +  
 +1 GROUND
 +2 DATA
 +3 NC
 +</code>
 +
 +<code>
 +modprobe w1_ds2431
 +echo "hello world" > /sys/bus/w1/devices/2d-00000de5d608/eeprom
 +cat /sys/bus/w1/devices/2d-00000de5d608/eeprom
 +hello world
 +</code>
 +
 === Resources === === Resources ===
 [[https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf|DS18B20 Thermometer]]\\ [[https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf|DS18B20 Thermometer]]\\
 [[https://datasheets.maximintegrated.com/en/ds/DS2431.pdf|DS2431 EEPROM]] [[https://datasheets.maximintegrated.com/en/ds/DS2431.pdf|DS2431 EEPROM]]