Lpc2000

I'm using the 48 pin LPC2102 and I'm having difficulty configuring 
P0.17 and P0.18. I want to use these pins as a general purpose 
output to provide a high and low voltage without any pull ups, the 
problem is that on the board I'm using these pins appear only to be 
able to give me an open drain output. 

From the Pin Configuration section (Chapter 6) of the User Manual 
both P0.17 and P0.18 are indicated to be "5v tolerant pad providing 
digital I/O functions with TTL levels and hysteresis and 10ns Slew 
rate control" so it would seem that these pins can provide the 
required output. Now although I'm configuring the pins as GPIO I 
realise that these pins are shared with the I2C functionality, 
however for the other pins which can share both GPIO and I2C (P0.2 
and P0.3) it is explicitly stated in the manual that they are "open-
drain 5 V tolerant digital I/O I2C-bus 400Khz specification pad, it 
requires external pull-up to provide an Output functionality"

Is the manual wrong?, have I misunderstood? or do I need to 
configure something apart from the PINSEL0/PINSEL1? Any Ideas?

--- In lpc2000@yahoogroups.com, "martymcflap" <martinjp@...> wrote:
>
> I'm using the 48 pin LPC2102 and I'm having difficulty configuring 
> P0.17 and P0.18. I want to use these pins as a general purpose 
> output to provide a high and low voltage without any pull ups, the 
> problem is that on the board I'm using these pins appear only to be 
> able to give me an open drain output. 
> 
> From the Pin Configuration section (Chapter 6) of the User Manual 
> both P0.17 and P0.18 are indicated to be "5v tolerant pad providing 
> digital I/O functions with TTL levels and hysteresis and 10ns Slew 
> rate control" so it would seem that these pins can provide the 
> required output. Now although I'm configuring the pins as GPIO I 
> realise that these pins are shared with the I2C functionality, 
> however for the other pins which can share both GPIO and I2C (P0.2 
> and P0.3) it is explicitly stated in the manual that they are "open-
> drain 5 V tolerant digital I/O I2C-bus 400Khz specification pad, it 
> requires external pull-up to provide an Output functionality"
> 
> Is the manual wrong?, have I misunderstood? or do I need to 
> configure something apart from the PINSEL0/PINSEL1? Any Ideas?

Most likely the manual is wrong.  For the LPC214x manual, Philips 
remembered the right footnote for both I2C ports.

Karl Olsen

----- Original Message ----- 

From: "martymcflap" <martinjp@...>
To: <lpc2000@yahoogroups.com>
Sent: Thursday, February 16, 2006 9:24 AM
Subject: [lpc2000] LPC210X P0.17 and P0.18 Operation.


> I'm using the 48 pin LPC2102 and I'm having difficulty configuring 
> P0.17 and P0.18. I want to use these pins as a general purpose 
> output to provide a high and low voltage without any pull ups, the 
> problem is that on the board I'm using these pins appear only to be 
> able to give me an open drain output. 
> 
>>From the Pin Configuration section (Chapter 6) of the User Manual 
> both P0.17 and P0.18 are indicated to be "5v tolerant pad providing 
> digital I/O functions with TTL levels and hysteresis and 10ns Slew 
> rate control" so it would seem that these pins can provide the 
> required output. Now although I'm configuring the pins as GPIO I 
> realise that these pins are shared with the I2C functionality, 
> however for the other pins which can share both GPIO and I2C (P0.2 
> and P0.3) it is explicitly stated in the manual that they are "open-
> drain 5 V tolerant digital I/O I2C-bus 400Khz specification pad, it 
> requires external pull-up to provide an Output functionality"
> 
> Is the manual wrong?, have I misunderstood? or do I need to 
> configure something apart from the PINSEL0/PINSEL1? Any Ideas?

IIRC, they need pull-ups on the LPC2106. The LPC2102 is probably the same.

Leon