NXT uC software 'tweak'

[finneykris]

Hi,

When I looked through the datasheets it seemed the processor can change it but although the processor can change it may be that the language or PCB will prevent it

It would be cool to have all the serial ports to be input.

Any ideas if it is possible and how?

[hassenplug]

Hi,

When I looked through the datasheets it seemed the processor can change it but although the processor can change it may be that the language or PCB will prevent it

It would be cool to have all the serial ports to be input.

Any ideas if it is possible and how?

Not sure about anyone else, but I don't quite understand what you're asking about. Please explain more...

[finneykris]

The software that is arleady installed in the rom in the microcontrollers of the NXT brick can be changed so that the connectors for the motors and sensors can all be set to be 'input', i found this by reading the datasheets of the two microcontrollers in question,

The ports are connected to registers inside of the microprocessors, you should be able to easly change the state of each bit in a register from input to output by editing the instructon set that is stored in the microcontroller already.

I am not sure if something on the motherboard or language/platform will prevent it from being possible, so does anybody know of anyything that willl prevent this from being possible?

maybe this is easier:

I may be use shift registers as IO expanders.
a LS165 or 74LS165? (i forget which number it is0) can be driven with existing IO, it would be parallel in serial out shift register and means I dont have to reconfigure the existing IO as the above idea suggests.

[mattallen37]

So, you want to use the "output" ports as I2C "input" ports?

[finneykris]

No, use three output pins, latch, data and clock toget 8 or 16 inputs

[mattallen37]

Well, the output pins (1 and 2) are set up to run motors. They are powered through an H-Bridge, and are at battery level voltages. They are strictly outputs, no way to read them.

The tacho lines (5 and 6) are inputs by default, and I don't know if physically they can be made outputs.

I'm not familiar with the type of serial you are talking about. Is it for parallel through 3 wires? Can you explain what you have in mind, both what you would build electronically, and also what you would do with it if it worked?

You can do almost anything (with time constraints) through the I2C ports. If you are looking for 8 or 16 logic (or even ADC) inputs, have you considered using a uC on an I2C bus? I know for a fact that the PICAXE 20X2 can add 10 ADC lines to the NXT with a very small amount of programming (I have done it, and have the programs).

[finneykris]

Ok I should step back ,im sure somebody else will/has done this some method, after thinking, I dont think I know enough to even theoretically do something like that. But thanks again for helping out

I am busy learning the basics of the PIC microcontroller architecture and workings but I am a little caught up in time over other hobbies and college.

I find it difficult to learn from books too so I use a desired chatroom.

I thought it was just a case of being able to change the pins connected to the connectors from input to output either externally or by changing the firmware.
the hardware might prevent that also., i did research the NXT's uC I/O capibilities.