Recent Posts

1

Microcontrollers / Re: A couple questions about Milk-V Duo boards

« Last post by SiliconWizard on Today at 10:27:21 pm »

Thanks! So, in terms of pure performance, at least from your benchmark, the C906 looks way behind a Cortex-M7 at the same clock freq, but not too far between a M7 @600MHz and C906@1GHz.

In terms of power draw, the "missing" info is whether it has any kind of sleep mode, which you can go to and resume from, either when running Linux, or baremetal.
62mA on "idle" is not bad for a CPU @1GHz, but the ability to put it in some standby mode drawing much less, and from which it could get out of within maybe less than 1s, would be nice. I haven't found the info so far and may have to order boards and figure it out myself.

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Test Equipment / Re: Old Fluke Multimeters

« Last post by Dave Wise on Today at 10:26:05 pm »

I finished my 8060A beep frequency mod.  Works great.  See topic "Low Frequency Continuity Beep for Fluke 8060A".

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Projects, Designs, and Technical Stuff / Re: Nichicon UPJ for switching power supplies - what's so special about these caps?

« Last post by mightyohm on Today at 10:25:43 pm »

I was curious if there was a specific characteristic of the UPJ that made it particularly suitable for switching power supplies, and whether that would imply a tradeoff to using the same caps in other applications. It sounds like it may be just marketing. Would love to hear from someone at Nichicon regarding this but they have ignored my request.

Regarding stability, it sounds like it is not a concern in this particular case.

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Projects, Designs, and Technical Stuff / MAX6399 - Undervoltage Lockout Not Working

« Last post by waymond91 on Today at 10:25:19 pm »

I have a circuit using the MAX6399 acting as an over-voltage and under-voltage lockout.
Here is a link to the part: https://www.digikey.com/en/htmldatasheets/production/2916090/0/0/1/max6399
I had one small hiccup where I got the gate pin wrong on the pcb, but I have bodged a to-220 onto the pads.

I was targetting an overvoltage lockout at 14.4V, and undervoltage at 11.6V. However, the overvoltage kicks in near 13.7V, and the undervoltage never fires.

I can measure the "OUT" and "OUT_SET" threshold voltages as I adjust the supply and see they are near their respective thresholds at the appropriate voltage.
For example, the undervoltage is near 0.5V at 11.6V, and the overvoltage is near 1.23V at about 14.4V

We had this behaviour after replacing the mosfet but before replacing the MAX6399. I have since replaced the max6399 and get the same behavior.

The Schematic


3D Board


Board with bodge mosfet AKA "The Bodgefet"

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Projects, Designs, and Technical Stuff / Re: Powering NeoPixels from 3.3V - Wrong but everyone does it?

« Last post by thm_w on Today at 10:25:05 pm »

Ignore the first response above.
We are not talking about logic levels, OP is talking about supply voltage specifically.

WS2812 just has a recommended range of 4.5 to 5.5V, no specified value I see. Blue Vf = 3.2 to 3.4V
WS2812B datasheet mentions 3.5 to 5.3V, but then later gives a recommended value of 4.5 to 5.5V. Blue/Green Vf = 3.0 to 3.4V
SK6812 mentions 4.5V, 5V, and 5.2V without giving a specific minimum. Blue/Green Vf is stated as 3.0 to 3.3V.

So no, you can't reliably have any of these working at 3.3V Vdd because the Vf of the LED could also be 3.3V or higher (as langwadt mentioned). You might get a bit of light but not the specified amount.

So my question is, can NeoPixel 3.3V operation be verified analytically, such that a design engineer can take an informed risk?

For example, perhaps it is known that the logic is 3.3V compatible CMOS but the LED Vf is 3.5V which would mean reliable operation at 3.3V but with compromised brightness / colour mixing.

If you don't care about brightness meeting spec then use SK6812 or something with a low Vf as possible.
But then whats the point of having a design without consistent brightness?

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Repair / Low Frequency Continuity Beep for Fluke 8060A

« Last post by Dave Wise on Today at 10:24:43 pm »

I love my 8060A handheld DMM's instant continuity beep, except I can't hear it.  It's approximately 2700Hz but I have a hearing loss that notches it out.  I modified my 8060A to output a lower frequency that I can hear.

The mod is a tiny daughterboard that mounts on the main board in place of Q6, a 2N3904 that drives piezo sounder LS1.  We need one flying wire to pick up +5.2V Vdd to power the microcontroller.

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Projects, Designs, and Technical Stuff / Re: "practically smallest" debug connector on tiny pcb

« Last post by ataradov on Today at 10:20:35 pm »

You don't need SWO for programming. It may be useful for debugging, but in most cases it is not worth it, especially if you already have debug UART.

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Microcontrollers / Re: RIP Z80

« Last post by SiliconWizard on Today at 10:20:01 pm »

Except if you are writing some generic RTOS, the core itself rarely matters as long as its meets the performance requirements you have. So, that's from the software POV.

The point, as some have said already, is more with the toolchains. If it's an ARM core, you can use mainline GCC for ARM targets (or LLVM), you can (usually) use generic JTAG/SWD probes, and so on. More odd architectures will usually require very specific vendor tools, which you'll be tied to (and which may be expensive). Whether this is an issue in your particular case, only you can answer.

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Projects, Designs, and Technical Stuff / Re: "practically smallest" debug connector on tiny pcb

« Last post by Wilson__ on Today at 10:12:16 pm »

many thanks.  very good thinking.  snap off to 0.1 inch connector and on board hole or poco pin pads at 0.05 inch

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Projects, Designs, and Technical Stuff / Re: "practically smallest" debug connector on tiny pcb

« Last post by Wilson__ on Today at 10:10:11 pm »

yes, many thanks.  0.05 inch through hole look good.  if one row, it can contact plate through hole with some bend force. swdio, swclk, gnd, vcc, nrst is 5 pins.  the new swo not tried before, is one more pin. Document says spy on the mcu but need graphic programming on the debug pc to extract useful data.  may not be too useful as now.  for luxery, uart tx, rx will be 8.