I have designed a pcb to run the LPC 2129 in the LQFP64(64 pin) package. As the system was too congested i decided to skip the 3.3 Vdda connection believing it to be required only for the ADC as a reference voltage. But the problem now is than on the 2 CAN controllers which i am using CAN1 is working fine while CAN 2 refuses to work. The pins just refuse to drive. There is no fault in the code as the similar code works on the demo board. There is no fault in the circuit or in the connections as i have personally checked all of the wire connections myself. There is no signal on the PINS on the microcontroller. Is this problem due to the non connection of the 3.3 Vdda pin ???
Connect a wire to the pin to get 3V3 there, problem either confirmed, or not, and you can go look at your code. Estimated time to perform 5 minutes, complexity low.
From the user manual UM10114:
Remark: When the ADC is not used, the VDDA pin must be connected to the power supply VDD(3V3), and pin VSSA must be grounded. These pins should not be left floating.
I scanned the user manual and could find anything suggesting anything else is on the VDDA/VSSA domain, not the CAN, not a Power-On-Reset (which would kill you on an STM32 BTW). I wouldn't had let it float, but can appreciate a beginner might. Not everyone is infallible.
Guess it was a beginer's mistake just that I wanted to minimise the number of connections to the IC as the board size i'm using is quite limited. There is no real mention of the use of the 3.3 Vdda other tha n a reference to the ADC but my delimma is HOW is CAN1 working in all of this ? but not CAN2 . Shouldn't both not work even the UART for that matter. UART is also working fine.
The Datasheet/User Manual tells you what you must do for the device to work as specified. If you deviate from those instructions, the behaviour is undefined.
"my delimma is HOW is CAN1 working in all of this ?"
That's really not a question to worry about; the behaviour is undefined - so anything can happen!
As already suggested, apply the 3V3 correctly and see what happens...
Applying 3.3 Vdda did not make a difference it still doesnt work
Then you have a number of alternatives to consider. - you have broken the hardware - your software is buggy (like having selected wrong multiplexing for CAN2 pins) - you have missed to turn on power for CAN2 - or does it too late in the code - you have a PCB error (beside the Vdda error) - ...
Thanks fr the support it was a PCB error after all.