Verifying Build Guide Changes from HW5 Rev3 to HW5 Rev5

[dwighthouse]

Hi there! I appreciate all the hard work everyone has put into this project. I'm a software engineer trying to get more into hardware. I'm a complete novice to the hardware side at this point, having done nothing more complex than working with LED strips before. Please be patient with my inexperience as I make sure I have the details correct before I begin building this device.

I have all the necessary parts for a HW5 Rev5 main board with the 6 slot Rev4 adapter board, which appear to be the latest versions available. I have the Clock Generator part, but I'm not doing the Automatic Voltage Selection, RTC, or Battery options. I will be using the standard two switch mode (on/off and 5V/3V).

As I reviewed the Kytor Industries build video again and the current build wiki page, I noticed one discrepancy: the closing of the J1 jumper.

I looked around and found this previous discussion:
#787

It seems to indicate that the jumper was intentionally removed (closed as part of the board design) in Rev5 and the step can be ignored, but I'm not certain because of my inexperience with the technical discussion going on in the thread. The build guide had previously stated that only Rev3 needed the jumper closed, but that part was removed so the step would still apply in Rev4 (which the OP had). Now I'm on Rev5 and it doesn't appear to have a J1 jumper at all.

1. Should I ignore the closing J1 jumper step in Rev5?
2. Does the build guide need to be updated so that the J1 jumper note only applies to Rev3 and Rev4, but not Rev5?

I'm also concerned about this note by Sanni:

The initial purpose of the 3 jumpers was to either run the Mega Pro at VCC, which switches between 3V and 5V(jumper J1 and jumper on LCD closed) or on fixed 5V(j1 and lcd jumper open, the other two jumpers closed) if the Arduino can't do 3V @16mhz.

If I'm understanding this correctly, if my j1 jumper is automatically closed due to my being on the Rev5 board, this means that I SHOULD close the R4 jumper on the LCD module (which is shown in the build guide and the video). Is my understanding correct? I'm not sure what "the other two jumpers" refer to in his statement.

3. Should the LCD module R4 jumper be closed in Rev5?
4. What are "the other two jumpers" referring to?

Thank you for your help.

[sanni]

1. You are correct, you can ignore the mentioning of the J1 jumper since you got a Rev 5 main PCB.
2. Updated, thanks for pointing it out.
3. Yes the jumper on the LCD module needs to be closed.
4. The initial main PCB design looked like this:

Back then there were two sets of jumpers.

• Closing the blue ones would always run the Mega 2560 Pro at 5V (as per datasheet) and the game slot on the other hand would be run at the voltage set by the voltage switch, so either at 5V or 3.3V, depending on the game cartridge that needs to be dumped.
• Closing the red ones instead would run the Mega 2560 Pro always at the same voltage as the cartridge slots. Which means for 3.3V systems the Mega 2560 Pro is getting undervolted, which about 10% of the Mega 2560 Pros can't do as the silicon quality varies similar to how you can undervolt CPUs or GPUs on PCs.

So that's what the mentioning of jumpers was referring to.

Now it was determined that option 1 with the blue jumpers is not good since there were issues occurring due to the fact the Arduino and the cartridge ran on different voltages, basically like communication errors because the Arduino would interpret high and low values different as the cartridge(e.g. when reflashing N64 repros). So this option was removed, first by changing the silk screen so that the blue set of jumpers were just labeled as test points, that way the PCB routing did not have to be changed and retested and then later with Rev.5 by properly removing all jumpers and make option 2 the default.

[dwighthouse]

Thanks for the thorough answer!