1Kernel driver nsa320_hwmon 2========================== 3 4Supported chips: 5 6 * Holtek HT46R065 microcontroller with onboard firmware that configures 7 8 it to act as a hardware monitor. 9 10 Prefix: 'nsa320' 11 12 Addresses scanned: none 13 14 Datasheet: Not available, driver was reverse engineered based upon the 15 16 Zyxel kernel source 17 18 19 20Author: 21 22 Adam Baker <linux@baker-net.org.uk> 23 24Description 25----------- 26 27This chip is known to be used in the Zyxel NSA320 and NSA325 NAS Units and 28also in some variants of the NSA310 but the driver has only been tested 29on the NSA320. In all of these devices it is connected to the same 3 GPIO 30lines which are used to provide chip select, clock and data lines. The 31interface behaves similarly to SPI but at much lower speeds than are normally 32used for SPI. 33 34Following each chip select pulse the chip will generate a single 32 bit word 35that contains 0x55 as a marker to indicate that data is being read correctly, 36followed by an 8 bit fan speed in 100s of RPM and a 16 bit temperature in 37tenths of a degree. 38 39 40sysfs-Interface 41--------------- 42 43============= ================= 44temp1_input temperature input 45fan1_input fan speed 46============= ================= 47 48Notes 49----- 50 51The access timings used in the driver are the same as used in the Zyxel 52provided kernel. Testing has shown that if the delay between chip select and 53the first clock pulse is reduced from 100 ms to just under 10ms then the chip 54will not produce any output. If the duration of either phase of the clock 55is reduced from 100 us to less than 15 us then data pulses are likely to be 56read twice corrupting the output. The above analysis is based upon a sample 57of one unit but suggests that the Zyxel provided delay values include a 58reasonable tolerance. 59 60The driver incorporates a limit that it will not check for updated values 61faster than once a second. This is because the hardware takes a relatively long 62time to read the data from the device and when it does it reads both temp and 63fan speed. As the most likely case for two accesses in quick succession is 64to read both of these values avoiding a second read delay is desirable. 65