I’ve designed a TX1 carrier and of all the things that may go wrong, the only thing that isn’t working is the fan (go figure something simple like this…or is it??). … and yes I know the fan is not normally running; only turning on when stressing the TX1 beyond some temperature threshold.
In the reference design there is a FAN_DISABLE GPIO signal that comes from a I2C-to-GPIO chip. This signal will force the FAN_PWM signal low and only goes high when a certain thermal threshold is crossed to start the fan. I did not include this disable signal on my carrier design. I assumed the FAN_PWM signal would only pulse when the fan should be spinning and otherwise stay low.
Other than the above disable signal my fan circuitry (FAN_PWM and FAN_TACH signals) is nearly identical to the reference design.
However when I boot the TX1 on my carrier, I do not see “tegra_fan” within /sys/kernel/debug/. I assume it doesn’t show “tegra_fan” become the software thinks there is no fan present.
Does anyone know how the software determines if the fan is present or not?