STM32F030 custom board

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ddrown
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STM32F030 custom board

Postby ddrown » Mon Oct 17, 2016 2:25 am

I created a devboard based on the STM32F030F4P6 chip because I wanted to experiment with a TCXO.

Image

I have details and more pictures here: stm32f030 devboard

I learned through this that 0603 parts are my limit. I've never done anything that small before, and they took some time to figure out how to handle them.

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ahull
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Re: STM32F030 custom board

Postby ahull » Mon Oct 17, 2016 1:44 pm

I'm impressed 0603 is where I start to sulk, if you so much as blink, they vanish. Sneeze, and you need to start again :D
I need to wear two pairs of x3 reading glasses just to have a sporting chance of placing them.
The hands are steady enough, but the eyesight is not quite what it was when I was 21 :roll:
- Andy Hull -

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ddrown
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Re: STM32F030 custom board

Postby ddrown » Mon Oct 17, 2016 5:04 pm

ahull wrote:I'm impressed 0603 is where I start to sulk, if you so much as blink, they vanish. Sneeze, and you need to start again :D
I need to wear two pairs of x3 reading glasses just to have a sporting chance of placing them.
The hands are steady enough, but the eyesight is not quite what it was when I was 21 :roll:


Heh, I had to use magnification to do this. The Tech Shop I do my work at has one on an arm with a built in light, which is very handy. I wouldn't have been able to do this without the magnification, my eyes aren't what they used to be either :)

They have something along these lines: http://www.magnifyingaids.com/store/ima ... 08_LRG.jpg

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RogerClark
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Re: STM32F030 custom board

Postby RogerClark » Mon Oct 17, 2016 9:09 pm

Like Andy, I bought a pair of x3 reading glasses for a few dollars and use them for all circuit work nowadays.

I also bought some x10 headgear from AliExpress, but its totally useless, as the focal distance is about 2cm, which makes it impractical to get that close to the OCB while wearing the contraption. It came with interchangable lenses going up to x50, but they are even less usable.

I also have a cheap USB microscope, but the lag on the display make it impractical to use for placing components, However its Ok for just doing inspection

A x10 jewellers loop is also very handy to have, especially for looking at markings on devices, and for doing inspections e.g. looking for solder bridges etc

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ahull
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Re: STM32F030 custom board

Postby ahull » Mon Oct 17, 2016 11:57 pm

I've also got one of these....
http://www.ebay.co.uk/itm/15X-Head-Band ... Sw~gRV0y~8
...very cheap, and fairly good, so long as you avoid poking your eye out while trying to figure out how to wear it.

Image

I've got a little more hair than the dummy in the photo, and the sprung steel band is inclined to grab your hair/beard/collar or fly off and land in your coffee. :roll:

They are good for inspection and very close up work, but the focal distance is too short to solder with, as you risk setting fire to your nasal hair. :lol:
- Andy Hull -

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RogerClark
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Re: STM32F030 custom board

Postby RogerClark » Tue Oct 18, 2016 12:06 am

I have some of these

http://www.ebay.co.uk/itm/Eye-Glasses-L ... SwQupXUTSp

Image

But they are useless, the lens diameter is too small.

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ddrown
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Re: STM32F030 custom board

Postby ddrown » Wed Oct 26, 2016 10:41 pm

10 days later, I have some data now. I hooked a GPS reciver's pulse per second (spec: within 10ns of UTC) to an input capture timer and saved cycle counts for every second. The timer is running (after a 4x PLL on the HSE) at 48MHz.

The frequency graph (in ppm or 1/1000000 units) is below. You can see it stayed within a 0.770 ppm range, which is acceptable for my TCXO, which has a spec of +/- 2.5ppm.

Image

I also created a video of how the frequency changed over time and its relationship to temperature. Each frame is 2 hours of data. The X's and +'s are the individual cycle counts compared to the room temperature. You can see there's not much frequency change with temperature change, it's mostly horizontal movement. There is however an slow drift upwards (maybe it's aging? The spec for aging for this TCXO is 1ppm/year). There's also a jump down at hour 297. I think I want to try this again with a better spec TCXO.

https://dan.drown.org/stm32/hourly-temp.webm

simonf
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Re: STM32F030 custom board

Postby simonf » Thu Oct 27, 2016 7:49 pm

Did you factor in the variations in vcc and accuracy on the temp measurement?

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ddrown
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Re: STM32F030 custom board

Postby ddrown » Thu Oct 27, 2016 9:23 pm

simonf wrote:Did you factor in the variations in vcc and accuracy on the temp measurement?


The temp measurement is from a LM75B, which claims 2C accuracy and 0.125C precision. I'm not too concerned about absolute accuracy from temperature but rather the accuracy of temperature movement, which I don't have a measurement for. I am sampling the temperature every second and using the average of 60 samples to try and limit the temperature measurement noise. I don't have any ideas on how to measure temperature any more accurately, so any suggestions would be welcome.

Voltage variation is something I need to measure, the TCXO claims +/- 0.2ppm for a +/- 5% Vdd change. I'd be surprised if the voltage changed that much, but I haven't measured it yet. Maybe I should hook my multimeter up to the regulator and take readings every few hours.

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ahull
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Re: STM32F030 custom board

Postby ahull » Thu Oct 27, 2016 10:59 pm

You might find this interesting, (and the comments are worth reading too).
Also this... which relates to a Maxim ADC, but the underlying methods are probably relevant to your use case.

There is also this... which might be of interest.
- Andy Hull -


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