Hi chronos users,
as far as I have seen in the ez430 chronos documentation and some videos on the web TI strongly advises to remove the battery of the watch module when the USB emulator is in use.
For the older chronos with black PCBs I do understand that because the positive pole of the battery is directly connected to watch modules VCC, which is coupled to the emulators VCC by a diode, so the lithium battery would be charged over USB what is expected to damage the battery.
The newer chronos with white PCBs have a protection circuit added that disconnects the battery from modules VCC by a P-channel Mosfet if an external voltage is applied to the debug port. When I tried to debug a program without the battery in it's holder, but with the USB emulator attached, I recognized that all buttons were not functional any more, I couldn't see any changes on the port inputs. That's because the buttons are connected over the metal back of the watch module directly to the batteries plus pole, which is disconnected from the internal VCC by the protection circuit, so no current can flow to pull the button inputs high.
From my point of view the situation now is as follows:
(1) For chronos with black PCBs the battery MUST be removed when the USB emulator is used to not damage the battery.
(2) For chronos with white PCBs the battery MUST stay in place when the USB emulator is used to hold the buttons functional. An update of the firmware is possible without battery, but debugging without using the buttons can be difficult ;-)
Could someone by so kind to prove or disprove that thesis?
Thanks in advance,