New RPL firmware for 50G - Revisited

[Han]

(02-19-2014 04:01 PM)Tugdual Wrote:  I mean for a starting point, what understanding of the official firmware do you have? Are you reverse engineering the existing one?

I can only speak for myself. I had actually started writing my own replacement ROM for the HP48 series, but that project has been put on hold indefinitely. I am fairly familiar with the ROM code for the HP48 series, as well as the HP42 series. I am also quite familiar with the hardware of the HP48 series. When I was working on a replacement ROM, I did actually disassemble the entire ROM contents, mainly to get a better understanding of the hardware interface. I got sidetracked when I finally decided to get the HP50G (very late, about 5~6 years after it was released!). I devoted a lot of my time toward updating Jazz so that it would work for the HP50G series. Recently, the Prime has taken up a lot of my free time :-)

Quote:Say I want to start my own custom firmware for the Prime, what shall be the effort?

That all depends on what you want the new firmware to do. If you don't care about backward compatibility, and want a custom firmware, then the only thing you really need to know is how the hardware works, and where certain hardware addresses are mapped. Once you have that, you can make your firmware behave however you like. A lot of the information is available in specification sheets for the various components on the PCB. I don't think there are any exotic (custom) chips, so you may be able to find all the info you need from googling.

You would need a cross compiler for the ARM chip -- unless you decide to do your firmware in ARM assembly.

One of our goals for a new HP50G firmware is to do clean-room implementation of RPL. So we will not be relying on any existing ROM code. Instead, our specifications are based off of RPLMAN.DOC.