AIn shows fixed value no matter the Input-mC damaged?

[Eggord]

Happy new Year

After i'm getting back to my little project this year and just solved the problem from last year i got a new one

I use the LPC4088 development board.

The the AIN0 and AIN1 now shows a fixed value no matter which voltage i apply to it. The AIN2 is fine(this is connected to a poti on the board).

 The reason might be that by an accident we applied a not appropriate voltage to these Inputs- meaning to high as well as negative (directly from the function generator, which was set wrongly)

Is it possible that this destroyed the AIN?

One shows value around 17 (so 0V) the other around 1011 from 4096.

Thanks in advance!!!

All the best,

Eggord

[frank_m]

> Is it possible that this destroyed the AIN?
Such things happen. I hope the board was not too expensive ...

This might be difficult to solve from the outside.

Did the same firmware work before ?
Do you have a second hardware to compare ?

Otherwise, the pin initialisation for the AIN0/1 GPIOs could be incorrect or incomplete, or you "destroy" the AIN0 / AIN1 results in the code (interrupt handler, I suppose) when reading out AIN2.

[Eggord]

Thanks for the fast reply!

I don't have another board and a new one would take months. Do you know where i can order one in stock?

I think the code is fine, since it used to work with the code. Also if i just change the AIN channels to 2 which it the onboard poti everything i works fine. But the other two AIN are clipped.

Eggord

[frank_m]

> Do you know where i can order one in stock?
Not really.  Funny question ... ;.)
But troubles to source electronic components are quite common nowadays.

> I think the code is fine, since it used to work with the code.
Which is the main point. If the same code worked before, the GPIO is probably damaged.
In most cases, an internal protective clamp diode blows out. Might have been negative surges with sufficient energy, or you connected a negative voltage.

Perhaps you can try to use other AINs of the MCU for your application.

And with said pins, you can try to initialize them as standard IO and toggle them.
If that works, the damage is probably limited to the analog section of said pins, and you could still use them as GPIO other assigned interface functionality.

[Eggord]

Hm...too bad. Maybe there is somebody here with a LPC4088 OEM on the shelf and doesn't need...

By internal you mean on the OEM board or the LPC4088 SOC itself? if it is on the board i might fix it.

By the way a maybe stupid question.:The LPC4088 has 8 AIN but the development board only reference 3 of them are the other just not available with the OEM board? if not, why? It would be great if i can just assign the other AIN to these GPIO.

Thank you a lot !

[frank_m]

> By internal you mean on the OEM board or the LPC4088 SOC itself?

I mean the silicon. Albeit it is only an assumption, MCU analogue input cicuitry is usually relatively sensitive to overvoltages or negative voltages.
You can check the schematics of your eval board, but I suspect there is not much protective circuitry. This is the way many eval boards are made.

Doing a short search, I suppose you speak about the board originally made by EA (Embedded Artists) which consists of a plugin OEM board, and a baseboard. EA does usually not publish schematics (only registered customers with login), but the board like quite "stuffed". Which leads me to the next point ...

> The LPC4088 has 8 AIN but the development board only reference 3 of them are the other just not > available with the OEM board? if not, why? It would be great if i can just assign the other AIN to these GPIO.

You would need to cross-check that with the datasheet (GPIOs with AIN functionality) and the schematics of your board.
But as stuffed as said (base-) board looks, the other GPIOs with possible AIN functionality are probably tied to other hardware like LCD, ext. memory or serial communication. That would almost certainly interfere with the analog functionality. Not sure if modifying the baseboard hardware would be an option.

This is why I usually prefer more "basic" boards, with most GPIOs routed to connectors. For which I make "custom specific" baseboards using veroboard when needed.

An alternative option would be an external ADC, possibly with SPI interface.