Any experience using STM32F042?

I’ve been looking at some very compact Arduino-derived boards, like the Digispark and Digispark Pro. I’d like to enable folks to make compact smart-gizmo’s, preferably even smaller than Maple-mini.

We don’t have anything as small as an ATtiny85.

However ST Micro do make some STM32’s in a TSSOP-20 package, comparable to the Digispark Pro.

I’ve been looking at the STM32F042F. Compared to an ATtiny, it is a ‘turbo-nutter-power’ device. It is one of the lower-cost STM32 parts; simple yet still has USB.

It looks like it’d reduce part-complexity significantly compared to a Maple-mini:

• ‘crystal-less’ USB. Its USB doesn’t need a crystal (and capacitors), and it can run using its internal oscillator, removing three (relatively expensive and ‘PCB hungry’) parts.
• an internal USB-pull-up resistor, removing the seven Maple-mini parts operating the USB-pull-up resistor.

Even better, the STM32F042 has a manufactured-in onboard USB bootloader, so there would be no need to own a USB-to-UART to load the initial bootloader.

So, I think it may be practical to have a compact PCB design, almost like ‘smart solder’.

It might be straightforward to bootstrap software because there are ST Nucleo boards with STM32F042s.

Does anyone have any experience or thoughts on using STM32F042F to make a reduced-size, reduced-cost, Maple-Mini/STM32duino?

There are some smaller STM32F103T based boards available but they are still a lot bigger than the digispark ( think there is a thread about the 103T board somewhere)

I’ve run the F103 libmaple based core on a STLink dongle which has a F101 and it worked fine.

But I don’t anything about the F042 device

The only commercial board I can find that uses this chip is the new Nano size Nucleo from STM

So the easiest way to see if it’s do’able is probably to splash out the $25 on a nucleo

Or get the TSSOP20 packaged version and make your own board using one of those breakout boards

This guy did his own board. But I guess you’ve already done a lot of searching and found this and a load of other information

http://andybrown.me.uk/2015/10/31/stm32f042dev/

RogerClark wrote:…
This guy did his own board. But I guess you’ve already done a lot of searching and found this and a load of other information

http://andybrown.me.uk/2015/10/31/stm32f042dev/

The DIL style package would make it easier to build from scratch, but I think the flash size may be a not of a problem, as libmaple takes around 16k for just a blink sketch. ( probably a bit less than 16k, but you know what I mean)

I think I will need to work out a way to solder STM32F103C s, as I have a number of projects which I need a small powerful MCU, but have limited space, so would like to put the STM32 onto a custom board.

I can get 10 F103C chips for around $15 on Aliexpress, which is not a bad deal.
I can get those minimum system dev boards aka Blue Pill for about $2.50, which are good value, but they are too big.

I’d love a digitstump size board with a stm32 on it..

Perhaps I better get designing !

I’ll be very interested if you design a TSSOP20 STM32F042 board.

We work with schools and colleges.
A 28-pin device, like an ATmega/Arduino is often too much for their projects. A digispark with 4 pins is a bit restricted.
I’d like to try a STM32 TSSOP20. A board should be about $5 in parts.

RogerClark wrote:
<…>
I think I will need to work out a way to solder STM32F103C s, as I have a number of projects which I need a small powerful MCU, but have limited space, so would like to put the STM32 onto a custom board.
<…>

Hi Ray

I do have a cheap chinese reflow oven (T-962), but I can’t get decent results with it, and I think its almost useless

I’m getting wildly different temperature readings from the two internal thermocouples, even though I’ve switched to using the Maxim thermocouple digital interface IC which is supposed to give much better results than the existing analog circuit.

I need to find time to replace the thermocouple that seems to give dodgy readings, but from what I’ve read online, that other people have been down that route and even with 4 thermocouples its still not working that well.

One guy fitted an internal fan, to circulate the air around, which supposedly makes the oven usable, but its a major mechanical modification to the oven, and I’d have to fabricate a lot of the parts myself, which would be difficult as I don’t have a lathe or very much else to make the parts I’d need.

The only good thing about the T-962 is the physical unit its self, e.g. the box with insulated internal compartment and a tray / drawer to put the PCB’s onto.

BTW. I had previously bought a toaster oven, and was going to modify it to be a reflow oven, but I then found the cost of the items needed to make it not loose loads of heat, were going to cost $$$, e.g. special gold heat resistant tape etc to cover the whole of the inside of the oven etc etc

I’m sure there is a solution to having a decent reflow oven at home, but at the moment I don’t have the time needed to either get the T-962 working or re-work the toaster oven as a viable reflow oven. As the key seems to be that the air needs to be moving, i.e it needs to be a convection reflow oven not a radiant reflow oven, but no one makes a cheap version

I reflow all my single sided boards on an electric hot plate like this link.

I bolted a 10mm aluminium plate to the top as a heat spreader though it may work fine without. Just apply solder paste with a syringe to all your pads place your components and then carefully place the board on the plate till the solder melts.

Actually, I know someone who has a heat plate soldering station, so I will see if that any better than my useless reflow oven

I found the article about the sand… in the responses.

https://www.sparkfun.com/tutorials/59

Re F0xx

I see that DirtyCheapPCB also have a breakout for the F0xx series. Looks good value, as you appear to get loads of small boards for the minimum $25 order.

Re:Reflow oven

Thanks Ray.

Even that $2500 oven seems to have issues with hotspots.

But you guys have spurred me on, and I will drag the reflow oven back out of a dusty corner of the shed / workshop and see if I can do anything to improve its poor performance.

BTW. With my reflow oven, I now remember , I tried using a hot air paint stripper gun, to blow air into the front of then oven, to see if moving the air around inside , make the thermocouples read similar values, but it didnt make any difference. One of them still read 20 deg lower than the other.

However it did give me an idea, that perhaps as well as using the internal IR heaters, I should remove the fan at the rear, that blows in cold air, and replace with the hot air gun.

But then I realised Id be better off using the hot air gun with my original toaster oven.
As it solves both the problem of the convection and also the lack of heating power ( excessive heat loss) on a normal toaster oven.

Of course this would mean that the oven will vent fumes all the time, but anyone soldering should be aware that there will be potentially nasty fumes

RogerClark wrote:
<…>
Of course this would mean that the oven will vent fumes all the time, but anyone soldering should be aware that there will be potentially nasty fumes

if its venting fumes, its venting heat

zmemw16 wrote:if its venting fumes, its venting heat

I have some of these generic Mini Ovens, e,g,:
http://www.amazon.co.uk/Sabichi-83913-M … B000L1KHYM

I’ve found them in the low-cost supermarkets ‘hardware isles’ like Aldi and Lidl. I’ve paid less than £20 (GBP) for one.

We’ve probably made dozens of boards this way. My chum Chris Evans has made many more than me. The boards have been both professional PCBs (solder mask, stencil, plating, etc.) and DIY etched with no solder mask.

This technique was taught to me by the inspiring Paul Gardiner (once of Finham Park School, Coventry, UK). He used it with 13-18yo school children with outstanding results.

RogerClark wrote:Re F0xx

I see that DirtyCheapPCB also have a breakout for the F0xx series. Looks good value, as you appear to get loads of small boards for the minimum $25 order.

@gbulmer

Do you operate your toaster oven manually to cook the boards ?

I bought one of those ovens a while ago and was going to add MCU control, but when I read the various articles on the web, they seemed to indicate that they don’t get hot enough unless you do some serious heat proofing

You guys make me feel like a Neanderthal. My SMD soldering station consists of a reasonably thick aluminum frying pan used on either the barbecue (if it’s nice outside and not windy), an electric skillet or the kitchen stove (if my wife’s not home). I apply paste on the PCB being worked on, place the components, put the PCB in the pan along with a scrap piece of PCB with some paste on top of it and put the pan on the heat source turned to maximum. When I see the paste on the scrap PCB start to melt I count to five, remove the pan from the heat and then remove the PCB’s from the pan to cool down. So far my success rate has been high enough that I haven’t tried anything more sophisticated.

Like that : https://www.youtube.com/watch?v=3drirgNktQg

RogerClark wrote:@gbulmer

Do you operate your toaster oven manually to cook the boards ?

martinayotte wrote:
Like that : https://www.youtube.com/watch?v=3drirgNktQg

umm

Mine has 1190W – 1420W printed on it..

But I have an inline power meter, and it read 1340W when I just turned the oven on.

Do you know how much power yours actually consumes, or was the 1.3kW written on it?

BTW. I’ve just had my T-962 reflow oven to pieces again on the bench and I replaced both thermocouples with new ones (albeit from eBay)

But as the temperature climbs above 100 deg, one probe starts to read a lot higher than the other.

I’ve actually not got both probes right next to each other (well about 1cm apart) and just off the base of the tray where you’d put the PCB

Starting bake with setpoint 200degC

Temp0, Temp1,
214.2, 186.8
214.5, 187.0

Mine has 1.3kW printed on it.

I have a “killowatt” so I can power it up (at the weekend), and report back.

If you only had one thermocouple, would you happily use your reflow oven?

Have you got an independent way to check temperature, e.g. some solder paste?

I don’t think thermocouples are renowned for their accuracy anyway.

http://thermocoupleinfo.com/thermocouple-accuracies.htm

You would probably need to calibrate each thermocouple against a known reference (boiling water, melting solder or whatever). You also need to ensure that all other electrical connections to the thermocouple, don’t also act as thermocouples

I have a varienty of thermocouples and various other ways to measure temperature, but I agree there is no way to know whether any of them are accurate unless i do some calibration.

The other problem is that the thermocouples seem to read similar temperatures up to 100 deg, so even using boiling water wont be much use.

I’d need to use something that has a boiling point, or melting point at around 150 deg, but I cant think if anything off the top of my head that fits the bill.

I guess my concern was that one part of the oven was getting substantially hotter than another, when in fact, it looks like its just an issue with the thermocouples

But as one thermocouple starts to read at least 30 deg more than the other, at 200 deg, Im also wondering how much temperature regulation i’m really getting, as the firmware averages the two therocouples.

BTW.

i have aready reflashed the firmware with some open source FW, and had to modify it to interface with the spi thermocouple interfaces.

So I could modify it further and add calibration tables for the thermocouples, but it sounds like i may as well just cook the pcbs in a fryingpan on the cooker in the kitchen, and get equally good results

RogerClark wrote:…
So I could modify it further and add calibration tables for the thermocouples, but it sounds like i may as well just cook the pcbs in a fryingpan on the cooker in the kitchen, and get equally good results

Hi Andy

Yes. I think that adding an internal fan would probably resolve the problems.

I know someone else has blogged, roughly, how they added a fan to this oven, but it was a little short on detail.

they seemed to remove the heat insulation from the top and cut a hole, then have an external motor, driving through a shaft into the hot part of the oven, directly above the middle of the tray.

this is probably the best location, but its challenging to build something that can withstand the 250 deg heat.
I have a feeling they just relied on the bearing in the motor, and had a tube through which the drive shaft entered the oven.

But I will need to find the postings can try to collect the parts will need to do the same thing.

RogerClark wrote:
<…>
But as one thermocouple starts to read at least 30 deg more than the other, at 200 deg, Im also wondering how much temperature regulation i’m really getting, as the firmware averages the two therocouples.

Hi Ray

I’m using 2 Max31855 modules

http://www.ebay.com/itm/MAX31855K-Therm … SwFMZWrxPf

Which are right next to each other. I’ve got the housing open and neither board is particularly close to a source of heat

But I’ll pull it all apart a bit, and use my IR thermometer to check both Max31855’s are roughly the the same temperature

I’d also previous fitted a DS18B20 probe to act as the cold junction sensor for when I was using the analog electronics on the original control board.

But as the sensor data is now coming in from the 31855’s, I’m not sure what the firmware is doing with that data.

Either way, if swap the termocouples over, the problem moves with the thermocouple, so I think the issue is the thermocouple.

I actually have more Max31855 modules as well, and the firmware https://github.com/UnifiedEngineering/T … provements can read up to 4 Max31855 inputs, so technically I could connect up 4 thermocouples at the same time.

But I can’t remember whether the code I wrote for the Arduino Pro Mini (I’m using as a SPI to I2C bridge) supports more than 2 channels, I have a feeling I could not reliably detect if a max31855 was attached, so I think I hard coded it to just operate on 2 channels.

The other problem, if I have to reflash either the oven firmware or the Arduino Pro mini firmware, is that I’ve changed PC’s recently, and stupidly I didn’t make a separate backup of the firmware (arrrgggh)

So I’ll have to reserect the old PC (put the old disk back it it, as its now running W10 on a new HD), and then retrieve the firmware

Yes… My bad, as they say…

I am a new to stm32arduino.

I have a project which I want to migrate over from a Atmel 328p , I have bought a STM32F030k6T6 which is the same size as the 328p.

I have put it on a board and need to know how to if possible program it via STM32arduino?

jimpx225 wrote:I am a new to stm32arduino.

I have a project which I want to migrate over from a Atmel 328p , I have bought a STM32F030k6T6 which is the same size as the 328p.

I have put it on a board and need to know how to if possible program it via STM32arduino?

thanks for the reply.

Its all new to me but i have seen an eclipse/ openocd solution but I have no idea where to start with C++, is there anyway of migrating .ino sketches back to C++?

Looking at your latest question, it reveals that you are new with almost everything (sorry to be a bit brutal here).
*.ino sketches is simply filename extension for Arduino, in the old days (version < 1.0), this extension was different, it was *.pde.
But all those files are actually C++, so there is no reason about trying to find a way to migrate them.
So, seeing such lack of knowledge, I would strongly suggest you (like Ray said) to start playing with a MapleMini F103 rather than trying to port the STM32 core to F042 by yourself.

jimpx225 wrote:thanks for the reply.

Its all new to me but i have seen an eclipse/ openocd solution but I have no idea where to start with C++, is there anyway of migrating .ino sketches back to C++?

martinayotte wrote:Looking at your latest question, it reveals that you are new with almost everything (sorry to be a bit brutal here).
*.ino sketches is simply filename extension for Arduino, in the old days (version < 1.0), this extension was different, it was *.pde.
But all those files are actually C++, so there is no reason about trying to find a way to migrate them.
So, seeing such lack of knowledge, I would strongly suggest you (like Ray said) to start playing with a MapleMini F103 rather than trying to port the STM32 core to F042 by yourself.

jimpx225 wrote:
I have seen the light that the F103 is the way forward , the second question regarding .INO file is the ease of pin assignment EG digitalWrite(PC13,HIGH); If there is some way of doing this in eclipse it would make life quicker.