NEW: HP 15C Collectors Edition

[Eric Rechlin]

(11-02-2023 05:00 AM)dmh Wrote:  Thanks for the detailed information and photos Eric !

A previous post mentioned a button was still used, which line has the button connected?

It appears the wiring is direct and not going through the chip at all now, is that correct?

So if you can roll your own pogo type connector could you could make a new cable the same way?

So, where do I get the firmware (original and patched) and what software is now required?

Thanks again.

The Reset button and Erase button are both still connected. You don't need Reset because you can just use the reset hole on the calculator instead, but the button is more convenient. It's connected in the same place as the old cable, which I believe is pin 2, which would be to the left of the black (ground) wire, lower left corner, in the last image above. I believe Erase is pin 6, which would be to the right of the black ground wire, lower right corner. It's also unchanged from the old cable.

Wiring is indeed direct, bypassing the chip. The chip was only used for the TTL to RS-232ish voltage level conversion. Since the new calculators speak USB directly there is no need for any level shifting.

As long as you have something to work for the pogo connector, which is the toughest part, you can make your own cable.

Software is just a newer version of the SAM-BA software used for programming the older calculators. I have been using version 2.14; I don't see that for download anywhere, but I do see version 2.16 is still available, so maybe you could use that. It still claims to support the sam4l chips so I assume it will work.

To flash the calculator, here are the directions I found worked best:

1. Install SAM-BA.

2. Remove the battery door from the calculator and plug in the 6-pin connector from the cable.

3. On the cable, hold down Erase, then press and release Reset, then release Erase. This just puts the calculator in USB linking mode. Unlike on the 20b/30b, this won't actually erase your firmware, so you can safely do this even if you fail to connect in the later steps.

4. Plug the USB connector from the cable to your PC.

5. Wait for it to detect as a USB Serial Device. Then check Device Manager for the COM number; usually I saw COM4 or COM5.


6. Start SAM-BA, make sure the right COM port is selected, and select at91sam4l-ek as the board type:


7. Click Connect. A new window will appear, where you must enter 0x04000 as the address, pick the ROM file to upload, and then click Send File:


8. After the file is done transferring (less than 10 seconds), press the Reset button on the cable (or use the reset hole on the calculator) and then turn the calculator on.

If you have a problem anywhere prior to the point where you click "Send File", pressing the Reset button will let you get back to the "Pr Error" display without losing the firmware. If a failure occurs after clicking "Send File", then your calculator may not operate until you can successfully load a new firmware.