I received one of the first “official” 100 Nano DSO’s not so long ago and had the pleasure of playing with it over the weekend. For testing I created a repeating waveform with 8 pulses of 20us duration (25 kHz) at 5 ms interval and levels at 0 to 5V.
[size=85]// Arduino program to generate test pattern on digital pin 3
cli(); // disable interrupts to avoid signal delays
DDRD|=_BV(PORTD3);
uint8_t i=0;
while (true) {
if (++i==16) {
_delay_us(5000);
i=0;
}/if/
_delay_us(20);
PIND|=_BV(PORTD3); // toggle pin 3
}/while/[/size]
For the tests I used trigger level at 2.36V, trigger sensitivity at approximately 1V and falling slope (firmware 2.01, 1x standard probes). When trying to trigger the test signal I found a number of issues as follows:
AUTO
At 50us/div I get a fairly stable signal pattern (occasionally it will shift left by one div or so) centered on the display.
- If I press R/S to HOLD however, the waveform will disappear and a steady 5V signal is displayed. Changing to RUN will again bring the signal back.
- Displayed frequency alternates between 960Hz and 25KC (T1/T2 set to match pattern duration) whereas a steady 25kHz was expected.
- At 20us/div the signal shifts to the right and becomes unstable (disappears, jumps left/right).
- At 10us/div and below it is no longer possible to observe the waveform/pulses.
- At higher ms/div I can observe the pattern groups, but they’re unstable in shape and position on the display.
NORM
Observations and issues are similar to that of AUTO.
SIGN (I assume this is “SING” as referred to in the manual)
At 50uS/div (and below) it appears to trigger (HOLD is displayed), but the display will typically show only a steady 5V signal.
- Pressing R/S will occasionally show the pattern, but apparently at random screen positions (left/right). Other times it will briefly show the pattern (when I release the R/S key) and then disappear.
- If I manage to capture the waveform on screen it will flicker even though the signal is on HOLD.
- At 20us/div or below I was not able to find any logic to what gets displayed.
- If I remove the signal source (probe to GND) and press R/S it will display “HOLD” and show the steady signal (I would prefer it to display “RUN” with no signal displayed in this case until it actually triggers.) When I reactivate the signal (probe back on signal pin), the pattern jumps left/right/disappears and apparently it no longer acts as a singular trigger.
X-position (T0)
With a steady waveform displayed, I can observe the display shifting left/right (the bottom indicator moves very slowly and it doesn’t appear to relate well to the actual pattern left/right shift). It is unclear to me how this setting affects the trigger point (is it for HOLD patterns only or does it apply also to continues trigger modes?). At one point I moved the X-position far left and the marker disappeared altogether and I also got some unexpected signal patterns displayed. A power on/off cycle was needed to resolve this.
Capture waveform to SD-card
On first time use (Windows XP/SP-3) reported the SD card as 3.7GB and I could only format it for 32-bit FAT. It appeared top work as such however and I copied the CONFIG.DAT file to the card. At some point during testing however (I tried saving waveforms) it was again reported as “unformatted” and this time with a 1.8GB capacity. I did a format (this time with FAT-16) and copied CONFIG.DAT onto the card again.
I created “FILE001.DAT” and “FILE002.DAT” (0 byte size). When I try to save waveforms however, nothing appears in the files (they remain at zero bytes). No error message however is displayed. If I choose a non existing number, the message “File NoPlace” is displayed.
I understand others have been able to capture waveforms and also of an application to convert these files to bitmaps. Is this application available for download?
The manual states that files “FILE000.DAT” through to “FILE255.DAT” can be used, the user interface however does not allow “000” to be selected.
Final comments
I’m concerned about not being able to properly trigger/display waveforms at 50 uS/div and below. 1 MHz sampling rate is already very limited as scopes go and not being able use the Nano at anywhere near this speed (Audio, Sonar, SPI, TWI, USART) makes it more of a toy than a useful instrument. Also with these apparently fundamental issues with triggering and calculations, I really don’t know if I can trust it for anything. My limited time for testing however may attribute to some of the issues observed and perhaps also there are issues you’re able to fix through firmware updates. On the positive side, I much like the size/portability and the prospect of it working in accordance with the specifications you have released.