Hello All, thanks for the great wealth of info thus far.
I also have a T4 Chinese clone, which I "upgraded" with a rotary encoder and upgraded the firmware to 1.12k (using a custom ISP cable connected to an USBASP adapter).
The clone has SMT resistors with 1% accuracy, the PCB is okay-ish, including a 2.5% Voltage ref and it's compliant to the newer version of the schematic.
I have the following questions:
1. After downloading the trunk, I could use the default MEGA328-T3-T4 .hex and .eep to upload the firmware, and it sort of works:
- the tester is now functional including the rotary encoder I added.
- calibration can be performed successfully, but:
Issues/Concerns:
Issue 1: Capacitor ESR is off - e.g. capacitors I used to read with a 0.1 - 0.2 ohm ESR now show as 0.00 Ohm ESR
Adding a .7 Ohm resistor in series with a 0.00 ESR capacitor yields a .35 Ohm ESR (that is off by .35 Ohm!!!).
Calibration was performed multiple times with both a "known good" very low ESR 2500 uF electrolytic as well as a 2uF ceramic (unknown quality). Really crappy caps (which used to read 2-3 Ohm, still show up with appreciable ESR, albeit I believe smaller)
Issue 2: Sometimes (especially when turning the rotary encoder during a measurement) I get the "Not Calibrated" message. If I restart the meter, the calibration is OK. Going in the menu, I can see the calibration data
2. I looked at the software, and in the Makefile, I could see the following config: CFLAGS += -DNO_AREF_CAP which is basically saying there is no 1nF cap at Aref. My board has one, so I would like to comment out the above. I could take the cap out, but it seems like a good thing to have, so would rather keep it, even if it slows down measurement some.
Issue is that, building the project with WinAvr yields 107% !!!! Flash utilization, thus I cannot flash the FW. I used the -O3 and -Os options, but no dice.
I have also downloaded the updated Atmel AVR toolchain and updated my WinAvr to the latest toolset, however in that case, I get an error related to EEPROM defines (__eerd_m328 or similar). I believe this is due to the EEPROM access functions.
Thus, please can you help me with the following:
1. Help troubleshoot the cause of the ESR discrepancy I see with the meter
2. Please point me in the right direction in order to compile the FW successfully (within the 32k of Flash available
)
Thank you!!!
If I can provide any additional info, please let me know, thank you!