I want to design and 3D-print an external frontlight mod for the TI-89 Titanium that takes up to 100mA of power @5V from the USB port and uses it to light a couple LEDs that make the display easier to read in dark conditions, and perhaps let a bit of light leak onto the keypad as well.

Can the TI-89 Titanium supply enough power to light up a couple LEDs out the USB port?

P.S. Side related question: I was wondering what is the minimum voltage that the Titanium can run on. Technicalc has some good info about HW1/2, but 3/4 are nowhere to be seen.

USB On-the-Go only guarantees 8 mA of current, so it's probably not the best way to get power.

Ah okay, thank you.

The TI-84 Plus has a 100 mA limit and the 89T's USB hardware is very similar if not the same. The real question is whether you can turn the power converter on, 'cause I'm not aware of much USB work being done on the 89T. It's certainly possible, but you might be on your own.

So the current delivery mechanisms have to be switched on specifically in assembly?

Edit: This is a duplicate reply generated by accident. If you're a moderator reading this, delete me please!

If the TI-89 has a Send( command like the TI-84 family, that might turn the USB on briefly. I was able to power a few things just by putting the Send( command in an infinite loop.

Ah, well in that case, I think this project would be impossible for practical purposes without opening the calculator up, which I am not willing to do due to the presence of a second ribbon cable on the side I'm scared of tearing. Thanks for the information everyone.

Yes, the 5 V output is not on all the time to save power, because the regulator would consume current just being on, possibly more than the CPU. The TI-84 Plus only draws 1 mA when idle!

Hello. My name is Jose and I have two ti89 titanium calculators.

I just registered to tell you that you can use the Titanium I/O port (2.5 mm jack) and a little resistor and a LOW CURRENT led 1mA. I have it working like this and it works perfectly. I bought my low current 1mA led from ebay.

Hope this helps. 🙂

Sorry for my English.

Thank you. I will see what I can do with this.

P.S. Welcome to Cemetech. Your English is fine.

Welcome, Jose! Out of curiosity, what are you using that LED for? 1mA sounds a bit low for illumination.

I use the low current 1mA led to play with the calculator in dark conditions. The 1mA led illuminates the screen and the keyboard perfectly. It is amazing.

1mA is not enough in sunlight conditions, but I don't need illumination in sunlight conditions. 😉