DSO NANO - how we users can impact next hardware design !!!

Products & Technology DSO Nano
#4

Dual channel! I don’t think there is a lot to be gained from going to interleaved sampling to get 2 MS/s on one channel. 1 MS/s is plenty to cover basic audio-frequency use and 2 MS/s isn’t going to suddenly make it suitable for high speed logic or RF.

What I would love to see is 2 input channels plus a function generator output. That way I could apply a test waveform to a circuit and compare the output. Ideally there would be a built-in sin / square / triangle generator plus the ability to load a arbitrary waveform from flash. I now use my laptop sound card as a function generator. That works fine, but the maximum frequency is limited. Also, since the nano is single channel only I can’t display both the test waveform and the output.

I know the enclosure is part of keeping it cheap, but I am not thrilled with the d-pad control. I very frequently hit left/right when I mean to hit up/down or vice versa. A set of more standard “soft buttons” on the right side of the screen plus value up-down controls would be a big improvement. If that is possible within the target price range I would buy a second one.

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#5

Either that or better firmware which clearly indicates what each button does. Perhaps popping up when a button is pressed and disappearing again after a delay.

#6

Put in a digital com port that is accessable to/by other TTL/CMOS devices; SPI, I2C, UART. I would like to mod the firmware to use the DSO nano as a display for some of my automotive products. The digital com port would also allow to add external peripherials to increase the functionality of the scope; logic analyzer, external SPI ADC, etc…

#7

You could include a usb->serial adapter driver in your custom firmware :slight_smile:

#8

As I just have to explain a Nano to an employee who wants to measure only a few things, and as I’m even not so fit in electronics, here is a proposal which would bring wider acceptance and higher volumes:

Implement an additional “[size=200]simple mode[/size]”, where the Nano works as easily as a voltmeter, but displaying an oscilloscope signal curve also. Somewhere in a corner of the display the digital numbers for voltage, maybe Vrms and may be frequency. Readable from a distance of about 1 meter.

[size=150]EVERY technician, no matter whether working with cars, washing machines, office machines and so on needs something like that, and every electronics engineer also if he has to solve simple tasks.[/size]

Like 50 years ago, a voltmeter and an oscilloscope from HP, but now on 5x11 cm² for less than 100 €. That’s about it!

PS: Nowadays you can buy such a multimeter with oscilloscope for 200 € to 300 €, but if you could do it with this little thing for the shirt pocket for about 100 €, that would be pretty nice.

#9

Wow, that almost sounds dangerous, nano != multimeter. I hope you are atleast using a X10 probe for your higher voltages multimeter adventures. Thats the thing with multimeters, you can plug them in almost everywhere without worries, most works with all voltages up to 1000 volts or so and any serious multimeter have all kinds of protective things that should protect you no mather how wrong you are using it, it blow up and hurt you etc. A oscilloscope you don’t plug in unless you atleast know what voltage range you are supposed to be in. My multimeter I would never substitute with my nano.

Be careful!

#10

Yes, you are right, totally. But I did not want to make my post longer so I waited for somebody to solve this problem. Of course I miss a x10 probe now, maybe with a little switch x1/x10. And of course there is a need for input protection. Sorry for misunderstanding: I did not want to create another multimeter or an oscilloscope for high voltage. My proposal is, to improve and simplify one of the most used functions in daily life (voltage in numbers and shape). This function is already implemented now, but - at the first glance - hidden very well under a lot of lines, colors and options.
My proposal is inspired by the small format of the NANO: when working on your table you can use a larger instrument with larger bandwith etc. But working outside with a pocket size instrument often means working under pressure and in poor conditions, and you will be glad to see just the most important without need of make settings.
I think, the topic is “how to improve the NANO” and that’s just a proposal. It was born by the fact that the NANO would not lie on my table in order to explain it to an employee if it wasn’t a little bit complicated.

#11

I Have a few ideas. I really like the idea of using those unused pins. a function generator would be great.
and spectrum analyser would be of use to many, especially those in audio feilds. but i really think one of the best things you could add is a mini serial terminal. so many MCU projects send debug info over serial. in its current state you could just change some software, but i don’t see why there couldn’t be a 2-way link. especially if it worked with SPI, which is used is so many projects. with 2 way communication(even if it was based on a very slow keypad where you scrolled to each letter) you could configure stuff on the fly that might otherwise require dragging a laptop or adding extra wasted stuff to your project, like switches.

This project has the potential to be a lot more then a normal dso with good software.

#12

Seems simple to me – how about adding the Openbench Logic Sniffer FPGA design as the probe backend? Then you’ve got a quite righteous portable… well… anything kit!
And as for the reconfigurable nature of the FPGA, well, let’s just say some folks will come up with clever & interesting hacks for a portable cortex+spartan3. (Portable Bus Pirate?)

Capture 50MHz+ waveforms on 32 channels
* 200Msps captures up to 100MHz waveforms on 16 channels
* 100Msps captures up to 50MHz waveforms on 32 channels

16 buffered channels, 5volt tolerant
* M74LCX16245DTR2G transceiver tolerates voltages from -0.5V to +7V.

Why struggle to implement a 2 channel upgrade when you have ready access to an inexpensive 100Mhz 16 channel via serial port design?

Do it. Do it. Slaughter your competition with a $139 16 channel 100Mhz NanoDSO/L. :smiley:

#13

I think it can fit in a “iphone” case, with 4.3" screen better to see and more internal space, but must be dual channel scope capable of doing FFT, and x-y tracing and if its possible add a kind of "SUMP + bus pirate " portable interface, possible it will have less channels but only the 16 buffered channels are good for me. Lol

technically and omap35xx ( ARM A8 + DSP CS64+) + Spartan3 are a fu** good “plataform” to make this work… But our tool won’t be less than U$150, nevertheless I think It Will Worth this value.

but now I’m thinking, what type of connector to use to bring out the channels of the sump + pirate bus, or How to doing it?

#14

:open_mouth: :open_mouth: :open_mouth:

I guess it is a HUGE mistake if we have overlooked this post! Thank you so much for posting the ideas, which are really beyond our wildest internal brainstorming. Current DSO nano is more a prototyping level device, It will be our responsibility and top priority to improve such be-loved product with community wit!

We might not be able to consolidate so many wonderful ideas into one ultimate super mega DSO, BUT it would be more fun to brew a basic portable platform with vast extensibility. By adding an efficient and stable API, you could easily modify and even load additional apps to extend the software functionality. We will create some wiki and SVN to host/Sponsor the projects for sure.

I will keep you guys posted for the schedule, and open for any other suggestions and inputs.

Thank you so much for the impacts! :slight_smile:

#15

Hi all, I just got my DSO Nano v 1.3 two days ago :smiley:. It took me a while to figure out how to disassemble it (hint use a razor or Xacto to gently peel off the front label, remove 6 small screws).

I already knew that the Battery Charger-Power Supply circuit was an issue. Yes there is a protection circuit built-in the battery, but charging with a Schottky diode and a 1 Ohm resistor will guaranty short battery life. I have designed a fix which actually cost less than the original circuit. This will require a change in the PCB. (I have tried to load this to here, but every format I try is rejected. it is available as a MS Word. doc, and PDF)

I have a question: The test waveform showing quite a bit of peaking. Why? (Capacitors C0, C5, C3A, C4A, C6A are not installed)

I have also been thinking about the input amplifier IC, TL082. This is not the best (it is really happier with more voltage on the +/- power pins, it is noisy, and it has limited bandwidth) for this use.

A differential amplifier would be much better. This would eliminate some noise and allow using shielded twisted pair wire (like that use in tie clip microphones) which would eliminate more noise. This would require that the tip and ring of the input connector be brought to the main board, which should be easy. I have some ICs in mind, one of which has programmable (serial) gain from 0 to >-50 dB.

A couple of capability questions: can you use smaller parts (i.e. QFN)? Many of the newer ICs are only available in smaller package.

Is SeeedStudio making the small PCB with the pushbuttons? It would be better to put the input amplifier there, where it can be easily shielded. Moving the amplifier here would also allow different versions (i.e. differential, AC-DC, single ended, multiplexed 2 channels, etc)

I saw a comment about storing different set-ups. This should be to the memory card (perhaps 8 memories). It would require choosing “Save Image” or “Save Set Up” when saving.

#16

Hi,

I just made a Jpeg of the files and it is attched
DSO Nano Fix.JPG

#17

Hi Shazam,

Long time ago, user manton & i commented a similar circuit in a forum thread. viewtopic.php?f=12&t=495&start=10

I think its the way to go.

#18

Hi Slimfish,

The circuit is from Microchip and Fairchild: “Li-Ion System Power Path Management Reference Design”, document # DS51746A, 2008, pages 5 & 12. The FET – Diode combination was made by Fairchild for this specific application (disconnect battery when external power is present).

The cost for both ICs: FDFMA2P853 and MCP73832 are $0.64 USD at DigiKey.com. For reference, the LTC4054 is $1.82.

I am an older analog hardware electrical engineer, who is always amazed by the fantastic things microcontroller designers and programmers can accomplish. Also amazing is the difficulty they have with analog circuits. I am willing to help Seeedstudio with the DSO Nano, since it is a fantastic product and they are generous with Open Source activities.

Shazam

#19

Hi Shazam,

i’m also willing to help in the DSO hardware redesign. This circuit could be a nice start, as the battery charger is a weak point in the DSO nano. Probably, the only drawback of this circuit are the switching times due to capacities and the dropout voltages when the battery is low (as XC6203 needs at least 300mV@200mA) . But, i don’t know if people at seedstudio are capable to test the proposed solutions (Freezing, ESP… any feedback?).

Slimfish

#20

Hi Slimfish,

I am not sure I understand your point.

With the minimum USB voltage of 4.5 V, the output to power switch is well over 4 V, allowing adequate margin for the 3.6V supply and the two regulator ICs:XC6206P302 and XC6206P332.

When operating from the battery, as long as there is more than 3.0V from the battery, all should be good. The 3.3 V regulator would not be regulating, but the 3.0V battery voltage will still pass through. The ST uController operates at 3V. The only use for the 3.3 V is the SD card. Many SD cards will work at 3.0 V, but many will not.

The 3.6V is used for the +/- 5V supply boost regulator SP3232. This, unlike many switched capacitor power circuits, has regulated outputs, regardless if the actual input voltage. I think using this IC is a bit of genius on the part of SeeedStudio. It is also the output buffer for the test signal, with a guaranteed rise and fall time into high capacitance loads.

Most importantly, if you want to discharge the battery to near 3.0 Volts, it will have a significantly shorter life.

Shazam

#21

Hi Shazan,

i’ll try to explain to you although i have only a couple of minutes right now.

When circuit is USB powered, no problem at all.

If circuit is battery powered, as there is some current consumption, there will be a voltage drop across transistor. Supposing transistor has 100 mOhm and circuit draws 200 mA => 200mV. If battery is only a bit discharged (say 3.5V) then the regulator (3.0V) is operating in its limits of regulation (not really, but near).

The SD card isn’t the problem here (many of them work in the 2.7V-3.6V range) nor the Cortex (2V-3.6V) but the ADC reference. ADC uses VDDA to reference the VREF+ so if battery voltage drops say 3.3V (as the current in the VDDA branch is lower), we are losing accuracy in the DSO readings.

Of course, i consider this a trade off and otherwise the circuit looks very good to me.

Slimfish

Note1: i agree that the SP3232 trick is a neat one, but the output regulation is far from ideal (no linear regulator inside, it uses a discontinous mode with a 5.5V treshold).

#22

Slimfish,

E=I*R, therefore: 0.200 Amps * 0.100 Ohms= 0.020 Volts. The Fairchild data sheet shows that with a gate voltage of -3.5 V the Rds is 0.100 Ohms.

Shazam

#23

Shazam,

you are absolutely right. I unfortunately shift the units.

Slimfish