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EEVBlog 121GW Multimeter Firmware Details

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gnif:
Figured this would be of interest to some, I was expecting to see the firmware that this meter came with to be encrypted with at the very least some very basic xor, but turns out the 'EEVBlog.bin' firmware on the SD card is just the plain firmware, with what looks like a calibration file appended to the end of it (cal.dat)


--- Code: ---geoff@sarah-xen:~/Projects/121GW$ arm-none-eabi-objdump -D -b binary -marm -Mforce-thumb EEVBlog.bin | head -n 21

EEVBlog.bin:     file format binary


Disassembly of section .data:

00000000 <.data>:
       0:       4b78            ldr     r3, [pc, #480]  ; (0x1e4)
       2:       2000            movs    r0, #0
       4:       2879            cmp     r0, #121        ; 0x79
       6:       0802            lsrs    r2, r0, #32
       8:       0e35            lsrs    r5, r6, #24
       a:       0802            lsrs    r2, r0, #32
       c:       0e37            lsrs    r7, r6, #24
       e:       0802            lsrs    r2, r0, #32
      10:       0e39            lsrs    r1, r7, #24
      12:       0802            lsrs    r2, r0, #32
      14:       0e3b            lsrs    r3, r7, #24
      16:       0802            lsrs    r2, r0, #32
      18:       0e3d            lsrs    r5, r7, #24
      1a:       0802            lsrs    r2, r0, #32
        ...

--- End code ---

To explain:


--- Code: ---0x20004b78 - The main stack pointer
0x08022879 - The reset vector (this is thumb, so the address is actually -1)
... etc

--- End code ---

I am yet to look more into this, but it's good news from the point of view of writing custom firmware for the meter.

dr.diesel:
That is good news!

Since we now have a FW thread, my 121 came with v1.01 and I've seen references to 1.02?  Considering the FW resides on the SDcard I guess someone with a 1.02 could post it for us on 1.01 to upgrade.

gnif:

--- Quote from: dr.diesel on January 12, 2018, 12:48:02 pm ---That is good news!

Since we now have a FW thread, my 121 came with v1.01 and I've seen references to 1.02?  Considering the FW resides on the SDcard I guess someone with a 1.02 could post it for us on 1.01 to upgrade.

--- End quote ---

Indeed, mine has 1.01 on it, it would be interesting to compare the two.

Iagash:

--- Quote from: gnif on January 12, 2018, 12:50:24 pm ---Indeed, mine has 1.01 on it, it would be interesting to compare the two.

--- End quote ---

I attached version U-1.02 as zip file (at least I hope, since it is from my sd-card).

I suggest not to upgrade from this file. It might contain cal-data only suitable for my meter.
Just use it to compare against your files.

amspire:
Gnif, from what you currently know, does it look like we can add our own firmware using the existing bootloader and binary update mechanism? In other words, can we load new experimental firmware and easily return to the official firmware?

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