Unlike Texas Instruments, whose graphing calculators have famously not made technological improvements in decades despite keeping the same price tag, HP has made a few more modern graphing calculators in the last few years. One of which is the HP Prime which boasts hardware from the mid-2010s including an ARM processor, a color screen, and rechargeable lithium battery. But despite this updated hardware it’s still using micro-USB for data and charging. [David] wanted to fix that by giving this calculator a USB-C port.
The first steps were disassembling the calculator case and removing the micro-USB port. The PCB is glued to the LCD screen which isn’t ideal, but he was able to work on it with everything attached. The parts are small enough to need a microscope, and with a hot air station he was quickly able to remove the USB port. His replacements from a generic online retailer were able to be soldered without much effort, but there was one major complication. The new USB-C ports didn’t account for the “On The Go” mode supported by micro-USB and were shorting a pin to ground which put the calculator into “host” mode instead of acting as a device. But using the microscope and cutting a trace on the PCB disabled this mode permanently and got the calculator working properly.
As far as modernizing calculators go, it seems like the HP Prime checks a lot of boxes, with the major downside that the LCD screen and more powerful processor means that the battery needs to be charged more often than the old TI calculators. Rather than carry a dongle around everywhere, [David] found this to be a much more efficient change to his trusty HP. If you’re still stuck using TI calculators, though, there are a few ways to modernize those as well like this build which adds a lithium battery or this one which ports a few Game Boy games to the platform.
My graphing calculator has a touch screen. It also makes phone calls and shows me HaD. It’s not allowed in most proctored testing scenarios though.
And how’s the keyfeel?
Probably slightly better than my fx7500g, and vastly better battery life! 3x CR2023 and about 8 hour life iirc
how is a USB c connector enough of an upgrade to go through all this? (though i did once spend a whole day adding a way to fake serial data for testing purposes using I2C on an Arduino slave.)
If you have no micro USB cable, you’re the proud owner of a calculator that isn’t broken but won’t work. This would solve that problem by keeping you with the cables that are actually still in production. USB-C cables seem to last a lot longer in my experience as well. I’ve still had a cheap one go bad, but that was the one provided by google, so … not a surprise. I can buy a USB-C cable at the convenience store, micro USB requires internet shopping or, much more difficult than this mod, -> cable rebuilding. Yuck.
i feel like i am swimming in micro usb cables — having bought so many for my various Arduino projects. i had no idea they were becoming as scarce as working SID chips.
Truth be told tho, USB-C isn’t old enough to be battle-tested. Micro is great, as long as it’s treated with care.
In my own (careful) uses, I’ve never had a micro fail me. But I have had a USB-C cable itself fail on a brand new tablet after 2 months. Thought it was the female connector on the tablet, was pretty upset. But when I tested another USB-C cable, even though I was sure the prob was how loose and wobbly the cable felt, the problem was solved. Nice, tight click when plugged in again. So why would a USB-C cable fail, even though it was so new? I dunno. But I’ve never had a micro cable itself ever fail like that.
Personally, I love the micro. Others will disagree. The ignorant and brutish can certainly do some damage with these connectors (like the upside down crowd), but I’ve never had any issues with them when treated with care.
Was doing this actually worth the effort? Probably not… But I really enjoyed the challenge, and now that I have a USB-C port, I will use it and appreciate having it. I also got some hands-on experience debugging various aspects of the USB protocol, and I feel that was worth my time.
My next goal is to replace the original LCD with a higher quality IPS panel. Again, it’s not actually worth the effort, but I’ll get to learn how to reverse engineer the LCD signals and design an interposer flex PCB, which I hope will be worthwhile experiences.
Exactly. It’s the journey, not the destination. Does this really need to be explained on hackaday? Everything here is basically because why on earth not?
One of the major reasons that TI hasn’t updated their design is that they can’t or shouldn’t.
Their customer base is almost entirely students, who will need to use them at least a few times during exams.
Being pre-approved for exam environments is basically their only selling point in an era where people have access to far more powerful general or specific calculation/scripting/compute software.
Why update your design when your customers are going to search for a specific model because that is what their syllabus requires?
I’m not sure what that USB C port is even going to do, since I have never encountered an approved calculator with a rechargeable battery.
Do they want a USB C cable for easier access to Tetris uploads? Because every exam I have ever taken that allowed calculators and NOT software on a computer, even at the graduate level, had a proctor wipe the calculators themselves before the exam.
Both the TI84+ CE and the HP Prime have rechargeable lithium batteries and they need to be recharged fairly often. They are exam-approved (at least for many major standardized tests in the US). The HP Prime has a special “exam mode” that proctors can set it to. Besides this use case, there is homework, personal calculations, and also professors who don’t mind these more powerful models of calculators.
Personally, I much prefer using a dedicated calculator when doing lots of calculations. I find it more convenient and tactile than a separate program on my computer or phone. But to each their own.
I’m a big fan of replacing the mircoA ports to USB C. So far my transplants have been, a handheld fur ball razer. A CPAP ozone germ killer hose device. A Xmas tree kit (2 so far). A game boy clone kit. My next two in the works will be a small handheld flashlight and an emergency light. Both will require a battery changes to lithium but it will be mostly a snap. My source of ports is Temu.
SEEMS to me that if you are skilled enough to adapt a C connector, you are smart enough to just build a C to micro A adapter cord.
My old Samsung S3 tablet had a damaged micro USB port. Other than that, it was a glorious piece of hardware.
If you do this kind of upgrade, just ensure the new connector is mechanically robust.