Changes between Version 74 and Version 75 of gsc


Ignore:
Timestamp:
01/20/2021 12:36:04 AM (21 months ago)
Author:
Bobby Jones
Comment:

Add info on manually calculating ADC values

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  • gsc

    v74 v75  
    297297[=#hwmon]
    298298== System Temperature and Voltage Monitor ==
    299 The GSC implements system voltage and temperature monitoring (similar to industry standard AD7418) at i2c slave address 0x29. For each analog to digital converter (ADC) input, the value can be read at a register offset. The register mapping differs depending on the version of the GSC:
     299The GSC implements system voltage and temperature monitoring (similar to industry standard AD7418) at i2c slave address {{{0x29}}}. For each analog to digital converter (ADC) input, the value can be read at a register offset. The register mapping differs depending on the version of the GSC:
    300300
    301301[=#hwmon_v3]
     
    333333|| ADC A31    =||= 0xA2 =||= Raw ADC value ^2^ ||
    334334 1. See [#fan fan] below
    335  2. Consult individual board hardware manual or the Linux device-tree for a description of what voltage rail this is and what voltage divider is applied in order to scale it. The Newport Linux kernel and BDK use information from the Linux Device-tree to scale and name these ADC's. Note also that Vin (Board Input voltage) is evaluated at the board's primary power supply input and offset by an estimated diode drop and thus may differ from your actual power supply within a volt or so.
     335 2. Consult individual board hardware manual or the Linux device-tree for a description of what voltage rail this is and what voltage divider is applied in order to scale it. Once scaled you can use {{{<scaled adc value> * 2500 / 4096}}} (2.5V ref/12 bit ADC) to calculate your ADC reading in mV. The Newport Linux kernel and BDK use information from the Linux Device-tree to scale and name these ADC's.
     336 3. Vin (Board Input voltage) is evaluated at the board's primary power supply input and offset by an estimated diode drop and thus may differ from your actual power supply within a volt or so.
    336337
    337338A Linux 'Hardware Monitor' ({{{hwmon}}}) driver is available  which provides simple standard access to the above temperature/voltage registers via sysfs. The arguments have been given labels which define the source. The user can “cat” the label to determine the source. The hwmon will be found in /sys/class/hwmon/hwmonx where x is a number. Check all hwmonx directories, starting with x=0 and then x=1 until identifying the correct hwmon where the values are contained.