Posted on May 17, 2011 at 11:50 3V/5V incompatibility at port P1 with (all?) the turbo series. The following phenomenon
has been observed with UPS3354D and UPSD3334D:
if a digital input at P1 is driven high (to VDD = 5V) by an external device, all analog
inputs are corrupted (pulled high through some internal resistors). This can be easily seen at the
DK3300-ELCD demo board:
1 - Make sure that a jumper is installed at ADC7 (header JP14).
2 - Use the ''Banking'' demo program from the CD (or the site).
3 - Run the PWM/ADC test. Observe the ADC reading going from 3FFH down to near 0.
4 - Using clips, connect a 3K resistor between ADC0 (JP14) and 5V at the M41ST87 connector.
5 - Now the ADC reading cannot go below 100H.
The non-turbo UPSD3254D has no problem in the same condition.
I sent a note to STmicro support more than one week ago, and I got no answer. Can somebody
confirm this issue. Mr Moderator, can I have your opinion?
Daniel
