| Guenter Roeck | b4c9c1a | 2014-01-24 22:25:33 -0800 | [diff] [blame] | 1 | Kernel driver adc128d818 |
| 2 | ======================== |
| 3 | |
| 4 | Supported chips: |
| 5 | * Texas Instruments ADC818D818 |
| 6 | Prefix: 'adc818d818' |
| 7 | Addresses scanned: I2C 0x1d, 0x1e, 0x1f, 0x2d, 0x2e, 0x2f |
| 8 | Datasheet: Publicly available at the TI website |
| 9 | http://www.ti.com/ |
| 10 | |
| 11 | Author: Guenter Roeck |
| 12 | |
| 13 | Description |
| 14 | ----------- |
| 15 | |
| 16 | This driver implements support for the Texas Instruments ADC128D818. |
| 17 | It is described as 'ADC System Monitor with Temperature Sensor'. |
| 18 | |
| 19 | The ADC128D818 implements one temperature sensor and seven voltage sensors. |
| 20 | |
| 21 | Temperatures are measured in degrees Celsius. There is one set of limits. |
| 22 | When the HOT Temperature Limit is crossed, this will cause an alarm that will |
| 23 | be reasserted until the temperature drops below the HOT Hysteresis. |
| 24 | Measurements are guaranteed between -55 and +125 degrees. The temperature |
| 25 | measurement has a resolution of 0.5 degrees; the limits have a resolution |
| 26 | of 1 degree. |
| 27 | |
| 28 | Voltage sensors (also known as IN sensors) report their values in volts. |
| 29 | An alarm is triggered if the voltage has crossed a programmable minimum |
| 30 | or maximum limit. Note that minimum in this case always means 'closest to |
| 31 | zero'; this is important for negative voltage measurements. All voltage |
| 32 | inputs can measure voltages between 0 and 2.55 volts, with a resolution |
| 33 | of 0.625 mV. |
| 34 | |
| 35 | If an alarm triggers, it will remain triggered until the hardware register |
| 36 | is read at least once. This means that the cause for the alarm may |
| 37 | already have disappeared by the time the alarm is read. The driver |
| 38 | caches the alarm status for each sensor until it is at least reported |
| 39 | once, to ensure that alarms are reported to user space. |
| 40 | |
| 41 | The ADC128D818 only updates its values approximately once per second; |
| 42 | reading it more often will do no harm, but will return 'old' values. |
| 43 | |
| 44 | In addition to the scanned address list, the chip can also be configured for |
| 45 | addresses 0x35 to 0x37. Those addresses are not scanned. You have to instantiate |
| 46 | the driver explicitly if the chip is configured for any of those addresses in |
| 47 | your system. |