NP-41 Emulator (may be)

[Chris Chung]

(01-11-2018 06:41 PM)everettr Wrote:  Thanks for the reply. I was unclear. I was just thinking more of something to basically "debounce" the battery, like a 10 microFarad capacitor. If the circuit can't see the intermittents from battery jiggle, then maybe you avoid the bootloaderish memory corruption, and life is okay.

That's a good idea, I will look into it.

I had finally found the problem w/ the bootloader corrupting FRAM space. It turned out that I had a few variables and they were allocated via the stack. Although I had setup the stack pointer to RAM area during initialization, accessing these variables sometimes corrupts memory (that is when the "reset" vector got tripped in succession in a short time, i.e. jiggling the battery). I don't understand why except its a timing problem but I am able to fix it by not using the stack for my variables. I had changed and now use absolute RAM locations from my bootloader variables and avoided the memory corruption issue.

In order to fix the shipped units, the bootloader has to be updated. I had created a new firmware image which will facilitate this. The steps are as follows:

• Download np41_180118.bin from here.
• Turn off unit via [ON] key.
• Attach USB-serial dongle. You may connect only Rx,Tx and Gnd as unit is already powered by a CR2032.
• Connect to PC.
• Turn [ON] the unit while holding the [SST] key. You will see "V00x ..." displayed. Before this message vanishes (in 3 seconds), press and hold the [USER] key, this will place unit into bootloader mode. LCD should become blank.
• Start TeraTerm and select correct serial port. Baud rate is 9600N81.
• Press any key and you should be greeted by a '?' character.
• Press '@' key and you should be greeted by an additional '>' character. Unit is ready to received np41_xxxxxx.bin firmware update.
• Select "File" -> "Send File.." from TeraTerm top menu bar.
• I would check the "binary" box 1st (lower left on the dialog pane).
• Select directory ("look in" field) and the correct file (np41_xxxxxx.bin) and hit "OPEN" button
• Transfer will start, wait for it to finish and give it another 1 or 2 seconds and remove unit from PC. Detach USB dongle.
• Now the firmware is updated, pressing [ON]-[ON] combo or [ON]-[<-] combo will bring back the emulation.
• We need to, however, update the bootloader as it causes the memory corruption problem.
• This is done by doing a new key-hold combo. Turn off unit and turn [ON] again while holding the 'B' [1/X] key (B for bootloader), this will copy a new copy of bootloader from the new firmware to the original bootloader location. You can do this a few times if you want to make sure. You can also enter bootloader mode again just to check. The prompt will be changed from "?>" to "BOOT?>".
  

Apart from the bootloader fix, a new key combo (warm start) w/ [ON]-'D' toggles the display mode between "fast" and "true".

If your unit is operating OK for now, you don't need to change the firmware / bootloader. There is not yet major feature updates. And if it fails in the future, you can send it back for fixing.
If you do not have the dongle or means to perform the firmware update, I can do it for you via mailing back the unit free.
If you perform the update and fails it, you can send the unit back and I will fix it for you free.

And when you want to send back your unit for fixing / repairing, I would prefer to wait until my new batch of PCB arrived and I have them tried out 1st. A
nd I want to migrate your units to the new and supposedly better PCB design.

If everything works OK for you, I can still migrate your unit to better PCBs later on for free. It is better for for me to fix all the problems and have a more stable platform before doing this.