Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 Kernel driver nsa320_hwmon 2 ========================== 3 4 Supported chips: 5 * Holtek HT46R065 microcontroller with onboard firmware that configures 6 it to act as a hardware monitor. 7 Prefix: 'nsa320' 8 Addresses scanned: none 9 Datasheet: Not available, driver was reverse engineered based upon the 10 Zyxel kernel source 11 12 Author: 13 Adam Baker <email@example.com> 14 15 Description 16 ----------- 17 18 This chip is known to be used in the Zyxel NSA320 and NSA325 NAS Units and 19 also in some variants of the NSA310 but the driver has only been tested 20 on the NSA320. In all of these devices it is connected to the same 3 GPIO 21 lines which are used to provide chip select, clock and data lines. The 22 interface behaves similarly to SPI but at much lower speeds than are normally 23 used for SPI. 24 25 Following each chip select pulse the chip will generate a single 32 bit word 26 that contains 0x55 as a marker to indicate that data is being read correctly, 27 followed by an 8 bit fan speed in 100s of RPM and a 16 bit temperature in 28 tenths of a degree. 29 30 31 sysfs-Interface 32 --------------- 33 34 temp1_input - temperature input 35 fan1_input - fan speed 36 37 Notes 38 ----- 39 40 The access timings used in the driver are the same as used in the Zyxel 41 provided kernel. Testing has shown that if the delay between chip select and 42 the first clock pulse is reduced from 100 ms to just under 10ms then the chip 43 will not produce any output. If the duration of either phase of the clock 44 is reduced from 100 us to less than 15 us then data pulses are likely to be 45 read twice corrupting the output. The above analysis is based upon a sample 46 of one unit but suggests that the Zyxel provided delay values include a 47 reasonable tolerance. 48 49 The driver incorporates a limit that it will not check for updated values 50 faster than once a second. This is because the hardware takes a relatively long 51 time to read the data from the device and when it does it reads both temp and 52 fan speed. As the most likely case for two accesses in quick succession is 53 to read both of these values avoiding a second read delay is desirable.