Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

If clk freq is reduced, display blinks...

Status
Not open for further replies.

mandar_mahajan

Full Member level 2
Joined
Jul 8, 2009
Messages
134
Helped
7
Reputation
14
Reaction score
5
Trophy points
1,298
Location
mumbai
Activity points
2,090
Hi all, I am using P89LPC938 with internal clock freq of 7.37MHz.
& interfacing a bare 4 backplane * 13 segment display with it.

My aim is to reduce the current consumption for prolong use of the battery.
So i have used the DIVM reg of it. Using this the currents drops by 2mA(DIVM = 1), 4mA (when DIVM = 4). But the display starts blinking...
I dont know why this is happening. I am displaying my adc value in while(1)
after every 300msec.

Any notes to improve my understanding would be of great help to me.
Thanks!
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
47,466
Helped
14,044
Reputation
28,343
Reaction score
12,696
Trophy points
1,393
Location
Bochum, Germany
Activity points
276,048
Apparently you have to adjust the display mux frequency. The answer is in your code.
 

mandar_mahajan

Full Member level 2
Joined
Jul 8, 2009
Messages
134
Helped
7
Reputation
14
Reaction score
5
Trophy points
1,298
Location
mumbai
Activity points
2,090
Hello FVM,
I do not get ur point. I have change the timer reload values accordingly.
 

snafflekid

Full Member level 4
Joined
May 9, 2007
Messages
214
Helped
31
Reputation
62
Reaction score
8
Trophy points
1,298
Location
USA
Activity points
2,644
Each digit of your display is connected to a single display driver for a brief time period through a signal multiplexer. A signal multiplexer connects each digit to the display driver sequentially which is usually faster than visual perception. When you lowered you clock frequency, you slowed the speed that the multiplexer cycles to each digit and you see the blinking.
 

mandar_mahajan

Full Member level 2
Joined
Jul 8, 2009
Messages
134
Helped
7
Reputation
14
Reaction score
5
Trophy points
1,298
Location
mumbai
Activity points
2,090
Yes this is the problem i am facing.
What i have done as a solution is, put some filters to display the adc contents.
this results in blink only when the no is changing, else it remains steady.

Any other solution??

Regards
mandar
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top