pic16f916 lcd driver and 7-segment display

joelinacio · Joined: 16 Sep 2004 Posts: 9 Location: Brasil

Is possible to use the internal lcd module to drive 7-segment displays in multiplexed mode? I don't have the 16f916 to test it. Thanks.

Ttelmah · Joined: 11 Mar 2010 Posts: 19368

That's a read the data sheet one....

Does depend on the actual layout of your display, but:

joelinacio · Joined: 16 Sep 2004 Posts: 9 Location: Brasil

I'm worry with the current. Lcd's have low consumption...what type? cathode or anode common?
http://circuitdigest.com/article/7-segment-display

temtronic · Posted: Wed Sep 07, 2016 5:28 pm

you'll have to use transistor buffers for the 'digit' lines.
good news is you're not the first guy who'se thought of it so
Use Google and you'll find a guy who did a similar setup for a 'watch'.

My concern is that it may be easier code to not use the LCD peripheral of the PIC. Many have 'muxed' 4 digit LED displays that way.

Jay

Ttelmah · Joined: 11 Mar 2010 Posts: 19368

I must admit I assumed you were talking about a 7 segment LCD. You don't say 'LED' anywhere.

No. Multiplexed LCD's have a stepped output voltage. Four steps for 1/4 mux. Not suitable to drive LED's.

Honestly use the peripheral for what it is designed for. If you want to drive multiplexed 7 segment LED's, then there have been loads of code examples here....

temtronic · Posted: Thu Sep 08, 2016 4:52 am

hmm..pretty sure I read in the datasheet that the PIC can be configured for different 'step voltage' ''formats", including basic 'on-off' mode. I've never played with one even though I bought raw LCD displays, sigh decades ago.
Too many projects..too little time.
Once the 2by16 LCD modules came out it's been easier all around(mfr/code/HW) to use them ! Now I just use 4x20 displays.With 'big character/number' capability it's a lot easier for me to read stuff across the room.

Jay

joelinacio · Joined: 16 Sep 2004 Posts: 9 Location: Brasil

I am using 7-segments led displays in project. I have the same project using 16f873. If possible, I will try to change to 916. The state machine to multiplex the 4 displays use a lot of resources...

temtronic · Posted: Thu Sep 08, 2016 9:59 am

One option to reduce 'resources' is to 'outsource' the display to a separate PIC ! Any 18 pin PIC will work, 11 pins for the 4 -7 segment displays and 1 for the UART to receive data from the 'master' PIC.
While it does add $1 to the project, you do get a 'stand alone' 4 digit display module that can be used for any other future projects, even a PC could send data to it !
This is what the mfrs that make the LCD modules have done, embedded a micro on their LCD unit to simplify connecting to 'anything'.

Jay

Ttelmah · Joined: 11 Mar 2010 Posts: 19368