Update Hardware PWM page

docs/helios64/fan.md

@@ -1,28 +0,0 @@
-## PWM Introduction
-
-Please kindly review the [pwm pages](/helios4/pwm) from the Helios4 device.
-Basically the PWM mechanism of Helios64 board is same with Helios4.
-
-## Fan Control Schematic
-
-![!Fan Control Schematic](img/fan/fan_control_schematic.png)
-
-**Remarks**
-
-| Description | Header P7 | Header P6 | Remarks |
-|-----------|---------|-----------|---------|
-| PWM pin | PWM0 | PWM1 | 5V tolerant |
-| SENSE pin | GPIO4_C5 | GPIO4_C7 | no kernel module/userspace apps that make use of this pin yet  |
-| PWM Frequency | 25 kHz | 25 kHz | defined in device tree |
-
-## Fan Specification in Helios64
-
-Coming Soon.
-
-## Use Case in Linux
-
-Coming Soon.
-
-!!! Notes
-       RPM readings in the PWM fans is not available in Helios64 board.
-

docs/helios64/pwm.md

@@ -0,0 +1,47 @@
+## PWM Introduction
+
+PWM, or pulse width modulation is a technique which allows us to adjust the average value of the voltage that’s going to the electronic device by varying duty cycle of the power at a fast rate.
+
+The term *duty cycle* describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on. When a digital signal is on half of the time and off the other half of the time, the digital signal has a duty cycle of 50% and resembles a "square" wave. When a digital signal spends more time in the on state than the off state, it has a duty cycle of >50%. When a digital signal spends more time in the off state than the on state, it has a duty cycle of <50%. Here is a pictorial that illustrates these three scenarios:
+
+![PWM duty cycle](/helios64/img/pwm/pwm_duty_cycle_graph.png)
+
+## PWM Fan Implementation
+
+### Type-A
+
+![Type A Curve](/helios64/img/pwm/fan_type_a_curve.jpg)
+
+### Type-B
+
+![Type B Curve](/helios64/img/pwm/fan_type_b_curve.jpg)
+
+### Type-C
+
+![Type C Curve](/helios64/img/pwm/fan_type_c_curve.jpg)
+
+
+## PWM Fan Schematic
+
+![!Fan Control Schematic](img/pwm/fan_control_schematic.png)
+
+**Remarks**
+
+| Description | Header P7 | Header P6 | Remarks |
+|-----------|---------|-----------|---------|
+| PWM pin | PWM0 | PWM1 | 5V tolerant |
+| SENSE pin | GPIO4_C5 | GPIO4_C7 | no kernel module/userspace apps that make use of this pin yet  |
+| PWM Frequency | 25 kHz | 25 kHz | defined in device tree |
+
+## PWM Fan Connector
+
+![Fan Connector](/helios4/img/pwm/fan_connector.png)
+
+Connector Pinout
+
+| Pin | Function | Wire Color |
+|-----|----------|------------|
+|  1  |    GND   |   Black    |
+|  2  |    12V   |   Red      |
+|  3  |   Sense  |   Yellow   |
+|  4  |  Control |   Blue     |

mkdocs.yml

@@ -79,7 +79,7 @@ nav:
     - Jumper: 'helios64/jumper.md'
     - LED : 'helios64/led.md'
     - M.2 : 'helios64/m2.md'
-    - PWM Fan : 'helios64/fan.md'
+    - PWM Fan : 'helios64/pwm.md'
     - RTC : 'helios64/rtc.md'
     - SATA : 'helios64/sata.md'
     - SPI : 'helios64/spi.md'