weak pullups for port B of 16F690 unable to work

[C0J]

Hi,

Have try to engage weak pullups for port B of 16F690
but unable to get it work.

The following is the code:

[RLScott]

Have you tried to put a voltmeter on RB4 to read what voltage is there? Divide and conquer!
_________________
Robert Scott
Real-Time Specialties
Embedded Systems Consulting

[Wayne_]

From the help

Syntax:
port_a_pullups (value)

port_b_pullups (value)

port_d_pullups (value)

port_e_pullups (value)

port_j_pullups (value)

port_x_pullups (upmask)

port_x_pullups (upmask, downmask)



Parameters:
value is TRUE or FALSE on most parts, some parts that allow pullups to be specified on individual pins permit an 8 bit int here, one bit for each port pin.

upmask for ports that permit pullups to be specified on a pin basis. This mask indicates what pins should have pullups activated. A 1 indicates the pullups is on.

downmask for ports that permit pulldowns to be specified on a pin basis. This mask indicates what pins should have pulldowns activated. A 1 indicates the pulldowns is on.


Your device allows for individual pins to be pulled up.
try using
port_b_pullups(0b11110000); // A 1 turns it on

[Guest]

Hi RLScott & Wayne_

Thanks for your advises

Hi Wayne_,

have try your method of "port_b_pullups(0b11110000);", it works


Hi RLScott,

have also measured the voltage of RB4 & the following is the result:
using "port_b_pullups(0b11110000);" RB4=4.62v

the odd part is, when i use back "port_b_pullups(TRUE);" RB4 initally is ~2v then slowly decreases

Thanks again,
CJ

[C0J]

i have previously forgotten to login,

Hi, Wayne_,

you mentioned about "From the help", mind telling me where is the help so that i can access it next time if i encounter other problems

Thanks,
CJ

[dyeatman]

Why not try the current CCS manual (June 2008) page 201?

[Wayne_]

I use the CCS PCW Compiler, I press F1 to bring up context sensitive help or if nothing is highlighted it just opens up help. You can also access it from the ? in the top right corner.