SEROUT in Open Mode with LCD
Hi All,
I have been using the parallax 2x16 LCD serial display quite successfully, but since I am working on a battery application, I wanted to add a power saving mode when the display is not needed. To do this I added a high side pnp transistor controlled by one I/O pin to turn off the +5v to the display. What I found was without somehow disabling the serial data into the display, voltage (and current) was "leaking" into the display module from the data input. I then tried to change the data from the BS2 SEROUT pin from driven mode to open mode. Now I have problems and the display is garbled.
Initially my driven commands looked something like:
SEROUT 15, 32, [noparse][[/noparse]17] since I was using 19.2 kbps
Using the conversion documented in the SEROUT help, I then changed to:
SEROUT 15, 49184, [noparse][[/noparse]17] since I wanted to continue using 19.2 kbps and an inverted mode with a pull down (open source)
Can anyone tell me what I am doing wrong?
Thanks,
Glenn
I have been using the parallax 2x16 LCD serial display quite successfully, but since I am working on a battery application, I wanted to add a power saving mode when the display is not needed. To do this I added a high side pnp transistor controlled by one I/O pin to turn off the +5v to the display. What I found was without somehow disabling the serial data into the display, voltage (and current) was "leaking" into the display module from the data input. I then tried to change the data from the BS2 SEROUT pin from driven mode to open mode. Now I have problems and the display is garbled.
Initially my driven commands looked something like:
SEROUT 15, 32, [noparse][[/noparse]17] since I was using 19.2 kbps
Using the conversion documented in the SEROUT help, I then changed to:
SEROUT 15, 49184, [noparse][[/noparse]17] since I wanted to continue using 19.2 kbps and an inverted mode with a pull down (open source)
Can anyone tell me what I am doing wrong?
Thanks,
Glenn
Comments
Have you determined that power consumption is still too much of an issue when you use the command to turn off the display? (DEC 21). I believe this command preserves what was on the screen and restores the display with DEC 22.
Rick
What I have found is that the display off command really doesn't have much effect on LCD power drain.
Glenn
Jeff T.
The way I thought I needed to go was with the inverted mode since I wanted the open source configuration (resistor to ground) otherwise I am still supplying current to the module via the pull up resistor; hence the inverted mode (32800 + 16384 = 49184). What do you think?
Glenn
Jeff T.
I had thought about that, but after your suggestion actually tried it. I just used the LOW 15 (not using any resistor) command to make sure there was no data going to the display module. When I wake everything up, my SEROUT commands take over and everything is fine. This way I save the 20mA that the display module uses when the program is in the power save mode.
I still am a little frustrated that I couldn't get the open mode to work the way I thought it should, but I'll leave that exercise for another day.
Thanks again for your responses.
Glenn