diff options
Diffstat (limited to 'kernel/Documentation/hwmon/pcf8591')
| -rw-r--r-- | kernel/Documentation/hwmon/pcf8591 | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/kernel/Documentation/hwmon/pcf8591 b/kernel/Documentation/hwmon/pcf8591 new file mode 100644 index 000000000..447c0702c --- /dev/null +++ b/kernel/Documentation/hwmon/pcf8591 @@ -0,0 +1,90 @@ +Kernel driver pcf8591 +===================== + +Supported chips: + * Philips/NXP PCF8591 + Prefix: 'pcf8591' + Addresses scanned: none + Datasheet: Publicly available at the NXP website + http://www.nxp.com/pip/PCF8591_6.html + +Authors: + Aurelien Jarno <aurelien@aurel32.net> + valuable contributions by Jan M. Sendler <sendler@sendler.de>, + Jean Delvare <jdelvare@suse.de> + + +Description +----------- + +The PCF8591 is an 8-bit A/D and D/A converter (4 analog inputs and one +analog output) for the I2C bus produced by Philips Semiconductors (now NXP). +It is designed to provide a byte I2C interface to up to 4 separate devices. + +The PCF8591 has 4 analog inputs programmable as single-ended or +differential inputs : +- mode 0 : four single ended inputs + Pins AIN0 to AIN3 are single ended inputs for channels 0 to 3 + +- mode 1 : three differential inputs + Pins AIN3 is the common negative differential input + Pins AIN0 to AIN2 are positive differential inputs for channels 0 to 2 + +- mode 2 : single ended and differential mixed + Pins AIN0 and AIN1 are single ended inputs for channels 0 and 1 + Pins AIN2 is the positive differential input for channel 3 + Pins AIN3 is the negative differential input for channel 3 + +- mode 3 : two differential inputs + Pins AIN0 is the positive differential input for channel 0 + Pins AIN1 is the negative differential input for channel 0 + Pins AIN2 is the positive differential input for channel 1 + Pins AIN3 is the negative differential input for channel 1 + +See the datasheet for details. + +Module parameters +----------------- + +* input_mode int + + Analog input mode: + 0 = four single ended inputs + 1 = three differential inputs + 2 = single ended and differential mixed + 3 = two differential inputs + + +Accessing PCF8591 via /sys interface +------------------------------------- + +The PCF8591 is plainly impossible to detect! Thus the driver won't even +try. You have to explicitly instantiate the device at the relevant +address (in the interval [0x48..0x4f]) either through platform data, or +using the sysfs interface. See Documentation/i2c/instantiating-devices +for details. + +Directories are being created for each instantiated PCF8591: + +/sys/bus/i2c/devices/<0>-<1>/ +where <0> is the bus the chip is connected to (e. g. i2c-0) +and <1> the chip address ([48..4f]) + +Inside these directories, there are such files: +in0_input, in1_input, in2_input, in3_input, out0_enable, out0_output, name + +Name contains chip name. + +The in0_input, in1_input, in2_input and in3_input files are RO. Reading gives +the value of the corresponding channel. Depending on the current analog inputs +configuration, files in2_input and in3_input may not exist. Values range +from 0 to 255 for single ended inputs and -128 to +127 for differential inputs +(8-bit ADC). + +The out0_enable file is RW. Reading gives "1" for analog output enabled and +"0" for analog output disabled. Writing accepts "0" and "1" accordingly. + +The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send +the value to the digital-to-analog converter. Note that a voltage will +only appears on AOUT pin if aout0_enable equals 1. Reading returns the last +value written. |