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+--- Thread: How do you connect PWM fan (3/4 pins) to this board (2 pin fan connector)? (/showthread.php?tid=11767)
How do you connect PWM fan (3/4 pins) to this board (2 pin fan connector)? - aleksei - 10-09-2020
PWM fan connector:
![[Image: gHnTGVe.jpg]](https://i.imgur.com/gHnTGVe.jpg)
RockPro64 "PWM controlled fan header":
![[Image: rTLOXue.jpg]](https://i.imgur.com/rTLOXue.jpg)
What do?
RE: How do you connect PWM fan (3/4 pins) to this board (2 pin fan connector)? - tllim - 10-12-2020
(10-09-2020, 02:09 AM)aleksei Wrote: Seriously, how?
Just use the Vcc and Gnd pins, make sure your fan is 12V type.
RE: How do you connect PWM fan (3/4 pins) to this board (2 pin fan connector)? - aleksei - 10-14-2020
(10-12-2020, 11:56 AM)tllim Wrote:That would spin the fan 100%. Where do you stick PWM and read wires?(10-09-2020, 02:09 AM)aleksei Wrote: Seriously, how?
Just use the Vcc and Gnd pins, make sure your fan is 12V type.
RE: How do you connect PWM fan (3/4 pins) to this board (2 pin fan connector)? - Gienek - 11-19-2020
Hello Aleksei,
Your fan has non-standard pin colors, so I am not completely sure whether this answer applies. But assuming, this fan complies to the popular specifications (e.g. here
or here), you have rather bad luck with ROCKPro64.
The standard 4-wire PWM fan requires 5 Volt PWM signal with frequency between 21 kHz and 28 kHz.
The PWM signal at connector J8 is designed for direct driving a 2-wire fan. It has 12 volt and low frequency (in the standard Linux kernels). The signal is generated from PWM_1 (GPIO4C6), so it is easy to change its frequency by accessing the registers directly. But I do not understand the circuit, which converts the GPIO signal to 12 volt. So I am not sure if it can run well with frequency beyond 21 kHz. Also you would need to convert it down to 5 volts, what makes such solution somehow offending. First shift from 3 V to 12 V, and then back to 5V... I have asked once in this forum, if it is possible to obtain this signal before it is shifted up (https://forum.pine64.org/showthread.php?tid=7877), but no answers.
Thus, when I hit this problem, I have implemented fan control in a separate Arduino PRO Mini board, which communicates with ROCKPro64 through UART. The Arduino uses very little power and allows me to read additional temperature sensor, which I placed in the housing box.
Sorry for not knowing a better solution for you.
Best regards,
Gienek.