Any debugging tips for why FanPico is not reading RPM?

[silicon-ghost]

The PWM and sensor functionality is working great and I have a nice fan curve loaded in the FanPico. I've got 4 FanPico boards and none are able to read the RPM signal of my fans. I'm using Noctua F12 PPC (Industrial). I checked with my oscilloscope while the fan is plugged into FanPico and I'm seeing ~44Hz; It's reasonably in the expected range for a 3000 RPM fan running at ~40% PWM.

When I measure the fan I do see the PWM value
meas:fan1?
39,0.0,0

I tried a generic AMD CPU fan still attached to a stock AMD Ryzen heatsink and did not get a RPM reading there either. I think I can exclude the Noctua as the problem.

It looks like the board is supplying 3.3V for the open collector in the fan.

FanPico 1.4.1 firmware (fanpico-0804-pico.uf2)

[tjko]

Is the "5V" (D4) LED lit? If not, check JP1 setting (Fanpico needs 12V either from MBFAN1 or AUX connector to power the level converters).

[tjko]

Since you have scope, can you check that you see tachometer signal going in on the pin3 on the fan connector?

Then check that you see the same signal at position "1" on the PCB (with Noctua fans you typically see 12V Peak-to-Peak signal since Noctua fans usually have 12V internal pull-up). If you don't see the tachometer signal, double check (re-flow) fan connector solder joints.

Next check position "2", there you should see the signal except that its limited to to about ~3.3V?

Next check U7 pin 4, you should see same signal as on earlier step.

Then check that you see the fan tachometer signal coming out (occasionally) from U7 pin 3.

Then check that same signal shows up on "GP26" pad.

Final check would be that there there is good connection from Pico to GP26 pad.

[silicon-ghost]

My apologies. I should have clarified more details.

I have a lab bench supply providing 12V on AUX. Nothing plugged in, draws about 36 mA. Adding the industrial fan at 40% PWM jumps to 66 mA.

D2, D4, D5, D8, D12, D16, D20, D23, D26, D29, D32 are all lit up.

FAN1 thru FAN8 jumpers are set to AUX. Main Power jumper set to AUX.

Measuring without USB plugged in:
TP1: 11.98 V
TP3: 5.05 V
TP4: 3.28 V
FAN1 PWR pin: 11.98 V

Position "2" measured on scope:

Position "1":

U7 Pin 4:

*** U7 Pin 3 has no activity.

I verified continuity (with power disconnected) from Pico GP26 to U7 Pin 3. I made sure to check from the part of the gold pad I did not solder since I used the castellated edge.

U7:

• is getting 3.3 Vcc on pin 16
• No traffic to address pins.

[silicon-ghost]

THAT is when I realized I had a PEBKAC error. When I ordered the boards from you on eBay I picked the "non-display" option and just assumed I was getting 0804 boards. The silkscreens clearly show it is the 0804D model and I loaded 0804 firmware. Doh!

Thanks much for the pictures. It explained why I was so confused staring at my printout of the 0804 schematics and didn't see a U7 block. ;)

[tjko]

I had not thought about that before, but yes indeed 0804 firmware probably "mostly" works on 0804D board, since only major difference is in how the fan tachometer signals are read.

[silicon-ghost]

FYI, the Industrial Noctuas (as you can see from my scope pics), don't tie to the 12V rail internally. They are relying on the 3.3V your board is providing.