Products > Test Equipment
New bench scope - Fnirsi 1014D, 7", 1GSa/s
pcprogrammer:
Some pictures I found that might be of help. Might have posted them earlier.
donwulff:
Hi thanks! That can be inhered from your well done schematics (Though I was initially confused because the signals of the JTAG footprint aren't named the same as the pins on the FPGA |O). And looking at the datasheets for the possible uses of the pins / register addresses.
I'm really, really hoping I don't have to solder anything on the legs of the main chips, if I can avoid it at all, with the reverse-engineering that's been done that should probably be way easier. I was going to ignore GD32E230 and let it be as it is at the start, but I suppose it might be easier to localize the protocol from that. Even if I somehow hit the legs on the processors, that wouldn't really be a repeatable hack for a lot of people. Getting extra pins from JTAG or in a pinch from the "Special IC" would indeed be preferable, IFF it turns out there's any benefit to that.
The optoisolated solid state relay COSMO KAQY214S must be a copy of Philips AQY214S, looking at the data-sheet main difference seems to be KAQY214 *claims* ON-resistance of 20 to 30 ohms, whereas the Philips one is 25-35 ohms. This would change the frequency response, probably for the worse. On the other hand, if a COSMO KAQY214S connected in parallel with the R62/R80 on the 1014D schematic, it should alter that from 150 ohms to about 18 ohms. According to the simulation on the Russian site ( https://www.eevblog.com/forum/testgear/fnirsi-1013d-100mhz-tablet-oscilloscope/msg3147914/#msg3147914 ) it should raise the low-pass filter for Nyquist/aliasing to around ~100MHz when the photodiode is driven (While maintaining the 400 V signal/1500V isolation) with minimum components/noise. Then again, I haven't independently verified the simulation, and it looks to me like it MIGHT apply mostly to AC-coupled mode, but the easiest solution is probably to just try ~20 ohm resistor in parallel once I get unmangled readings from the ADC with the new firmware (And maybe OPA356's to get faster rise time).
Speaking of MS5351M clock-generator, looking at the board on thermal camera, that thing's running at 50C+ hottest thing on the board while everything seems to assume it should be ran at room temperature. I don't think there's floating inputs or anything possible, so just normal? https://www.qrp-labs.com/synth/ms5351m.html says it's Si5351A clone, which is presumably where I'll find the I2C protocol/commands. Something like https://media.digikey.com/pdf/Data%20Sheets/Silicon%20Laboratories%20PDFs/Si5351A_B_C.pdf Of course reverse-engineering source can confirm values.
Firmware needs straight-forward Windows installer, although I'm wondering if there's different sizes of SD cards, too. It's kind of shame they didn't make the SD card external if they were going with one...
pcprogrammer:
I looked back at the schematics and noticed that I did not connect the JTAG connector labels to the FPGA :palm:
The JTAG pins are dedicated and can't be used as a normal IO pin, so no luck there. I can understand not wanting to solder any wires to the IC's as part of a new setup to be widely used. Similar to the reason for not making a new FPGA programming for it.
The two pins used for the special IC, are available and can easily be connected to on the provisioned header. Only problem is the IC on the lines.
The datasheet of the MS5351 is in the repository, but there is no programming info in it, so I guess it needs to come from the Si5351 manuals, and try to find it in the firmware.
I'm no expert on analog stuff, so can't really help on that. I had some electronics education and worked in the field a bit, but mostly digital and moved on to programming. A couple of years back I returned to the electronics hobby with an emphasis on microcontroller projects. Digital audio synthesis has my interest, and to have a small scope near my computer was the reason for buying the 1013D. It arrived with a problem in the touch panel, and that is what got the reverse engineering hobby started.
donwulff:
Same, same. That's why I'm asking ;) Though analog electronics comes up a whole lot in digital/embedded, but generally not OpAmp frontends. I think I was looking for an affordable hobby scope for learning/experimenting that I can use for anything without having to worry about breaking it on AliExpress, and you gotta admit the 1013D/1014D specs catch the eye. But with the Chinese stores, well I'd say 110% of them qualify as some kind of scam, starting with how every entry lists the price of some wire or something and not the expensive thing in the listing, the affordable thing is sold out, shipping is more than the product etc. but the one thing is you typically get the same thing that everyone else. So you have to Google it, and this thread comes up, and I know about the 30-40MHz useable bandwidth etc. (However I'll not this is still fairly confusing, because the rule of thumb is that any scope is only professionally suitable for signals 1/5th the bandwith on the front plate, so by that FNIRSI would be for ~20MHz signals. That said sampling rate is big deal, making it 40MHz plate equivalent, and thus maybe 8MHz real? And let's not talk about the sensitivity, which makes it indicator rather than signal integrity. But let's be honest that's MOST of what one would use a scope for.). The irony is it's going about open firmware for it, but turns out it doesn't work on the 1014D ;) That's fine though, if I was going to play with the firmware, I might just as well try to make it work.
I'm trying to actually figure out Evi's ground offset mod at https://www.eevblog.com/forum/testgear/fnirsi-1013d-100mhz-tablet-oscilloscope/msg4536116/#msg4536116 - the schematic shows the negative reference going to pin 2 of the ADC. So that must be biasing the signal to -1.125V with -2.5V ref, but seems like that would flatten the signal, if I'm following double the rise-time for the OpAmp although probably reduce noise at the ADC? Though I suppose the first question is do I need / benefit from that at all. Also looking at that board picture, that's a whole lot of wires acting as antennas, which I'm worried for any modifications.
I think people would be fine, even eager to make small changes to the scope. If the new firmware works better than original, I'm sure anyone actually using a scope anyway could handle desoldering the chip. Even without that I guess that gives one in and (more importantly) one out signal without breaking anything, as long as the FPGA can be replaced. Of course, still need cheap SPI programmer, and something to connect the IO's to. But yeah, yeah, let's see if there's any point to that.
pcprogrammer:
The 1014D has the advantage of the FPGA JTAG connector. It is possible to program the FLASH with the Anlogic IDE and the JTAG interface I wrote about earlier.
About the mod of evi, yes it could bring some noise into the signal. Though with the sensitivity as is don't think it will be a big problem. The ground thing is a problem when you connect the USB interface and have the probe ground on the same ground as the computer. That would be solved with the mod.
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