Products > Test Equipment

New handheld scope+DMM, Fnirsi 2C23T, 2ch, 10MHz/50MSps (Nov 2023)

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Kaluluka:
Hi!
I just got one and it has HW:04 but Firmware shows 2.1.0, not 2.0.1....

pilatomic:
Hello,

So I've been playing around with this device for a few days, and even if it certainly has its flaws, I quite like it as a cheap device I can move around.
The single shot bug was a deal-breaker for me, so I took a look at the firmware in Ghidra in an attempt to fix it.

First, I found a few features that missing from the manual  :
- There is a scope calibration function (DC offset nulling ?) engaged by long pressing "AUTO" in scope mode.
- Long pressing the center button in scope mode moves the traces to their default position.
- Long pressing CH1 and CH2 in multimeter modes enter some calibration mode (didnt try it, I dont want to mess the calibration on mine)

Then I was able to locate the issue with the single mode trigger :
Where I was expecting some sort of indexing issue, I found out they actively zero the sampling buffer before the trigger point !! (see attached picture)
Not sure what they had in mind when they wrote that, but I was able to make the code jump over that "feature" with a single byte change in the firmware.
I also changed the version string from 2.0.2 to P2.0.3 to make it clear what firmware the device is running

You'll find the patched firmware attached to this message, along with 2 screenshots showing the change of behavior from Fnirsi original firmware (2.0.2) to my patched version (P2.0.3)
TRY IT AT YOUR OWN RISK. I am not responsible for any bricked device.
It still doesnt make the single trigger mode perfect, as it samples a relatively low percentage of the time, so it easily misses the trigger point.
I might be able to prevent it to trigger entirely if the trigger point is not in the sampling buffer, but I feel it might look misleading.

To install the new firmware, hold the MENU button before pressing the POWER button (bootloader mode), then plug the device to a PC, and drop the firmware in the newly found USB disk.
If anything goes wrong, you can insert a pin in the hole on the side to reset it, re-enter the bootloader mode, and flash the original firmware back.

Feel free to leave any feedback !

dibu:
Nice found, i'm interested in making a completely open source firmware for it, it looks like you have more of the SW decoded, more functions, variables, i still have many functions like osci_channel_something, and only very few variables decoded. I would be very interested in your ghidra project if you want to share it.

tunk:

--- Quote from: dibu on June 17, 2024, 02:17:51 pm ---Nice found, i'm interested in making a completely open source firmware for it, it looks like you have more of the SW decoded, more functions, variables, i still have many functions like osci_channel_something, and only very few variables decoded. I would be very interested in your ghidra project if you want to share it.

--- End quote ---
EEVblog user pcprogrammer has created alternative firmware for the 1013d and
1014d. If the hardware is similar, then you might use his firmware as a starting point:
https://www.eevblog.com/forum/projects/reverse-engineering-the-fnirsi-1014d/
https://github.com/pecostm32/FNIRSI_1013D_Firmware

dibu:
i know about this project, and plan to buy the 1013d also at some point, just for the open sw, however i think these are very different from from a hw point of view, this scope-mm is much more limited, tiny cortex-m4 mcu and tiny fpga. But some SW components could be similar, both use ChaN FatFs, graphic lib is somewhat similar, font handling maybe, low level stuff here is from the AT32 HAL, it would be a good starting point overall.

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