How can I tell if the display is fired up and ready to receive commands? Do I just have to time it and program in a fixed delay? That just seems like the wrong way to do it...
Determining if display is started up
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dannysauer
- LCD?
- Posts: 8
- Joined: Mon Dec 12, 2005 11:53 am
- Location: Lincoln, IL
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Determining if display is started up
I'm controlling a VK204-25 over RS232 with a PIC 16F688 (hooray for a built-in UART) running at 8MHz - and a Max232cpe. The PIC starts up way before the display, so I have to pause for some period of time before I can start sending display data over - but I don't know exactly what that time is. The manual makes some mention of "the purpose of ACK," but then doesn't talk about how to actually get the display to ACK receipt of a command, what format that would be, or anything like that.
How can I tell if the display is fired up and ready to receive commands? Do I just have to time it and program in a fixed delay? That just seems like the wrong way to do it...
How can I tell if the display is fired up and ready to receive commands? Do I just have to time it and program in a fixed delay? That just seems like the wrong way to do it...
Hello dannysauer,
Thank you for your post. Unfortunately there is no indication that comes out from the display to signal that it is ready for communication. The ACK that is described in the manual is referring to I2C communication protocol.
You mentioned that your controller (PIC) is powered up before the display? This means then that the display is powered from a different power supply? Please take into consideration the time it takes for that power supply to completely power up; as for the display, from the time of stable power to being able to communicate is around 500ms.
Thank you for your post. Unfortunately there is no indication that comes out from the display to signal that it is ready for communication. The ACK that is described in the manual is referring to I2C communication protocol.
You mentioned that your controller (PIC) is powered up before the display? This means then that the display is powered from a different power supply? Please take into consideration the time it takes for that power supply to completely power up; as for the display, from the time of stable power to being able to communicate is around 500ms.
Raquel Malinis
Design and Development
Matrix Orbital
Design and Development
Matrix Orbital
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dannysauer
- LCD?
- Posts: 8
- Joined: Mon Dec 12, 2005 11:53 am
- Location: Lincoln, IL
- Contact:
No, both are powered up simultaneously from the same power supply, but the PIC is up and has run through the initialization sequence (configuring all of the inputs, the baud rate, etc) significantly faster than the display appears ready to accept commands.
Maybe I can set the display to automatically send keypresses, connect a couple of the keypad inputs to a GPIO (maybe connect them through a transistor) or something, and repeatedly tell the display to enable the GPIO until I receive the corresponding keypress? I'd short two of the keypad pins permanently, but that would probably not be so good if I wanted to actually *use* the keypad later. Which I do.
Or maybe connect one of the GPIOs on the display to an input on the PIC, and repeatedly tell the display to enable the GPIO until that pin goes high on the PIC? That might work... The GPIOs are just 5V (presuming the display is powered by 5V), right?
Ohh, even better, I could query the display for its identity over and over until I receive a reply. That wouldn't require any extra wires. Maybe I'll do that.'
Sorry for the "stream of conciousness" post - but it's easier to think when I'm typing, for some reason.
Maybe I can set the display to automatically send keypresses, connect a couple of the keypad inputs to a GPIO (maybe connect them through a transistor) or something, and repeatedly tell the display to enable the GPIO until I receive the corresponding keypress? I'd short two of the keypad pins permanently, but that would probably not be so good if I wanted to actually *use* the keypad later. Which I do.
Or maybe connect one of the GPIOs on the display to an input on the PIC, and repeatedly tell the display to enable the GPIO until that pin goes high on the PIC? That might work... The GPIOs are just 5V (presuming the display is powered by 5V), right?
Ohh, even better, I could query the display for its identity over and over until I receive a reply. That wouldn't require any extra wires. Maybe I'll do that.'
Sorry for the "stream of conciousness" post - but it's easier to think when I'm typing, for some reason.
Hi dannysauer,
I was going to say query the display until I read the last part of your post. Yes, the best thing to do is to query the display. Say for example, send cmd 254 55 and it should reply its module type which is 0x0F for the VK204-25 that you have. This of course is an indication that it is indeed ready to communicate.
Please let me know how it turns out.
I was going to say query the display until I read the last part of your post. Yes, the best thing to do is to query the display. Say for example, send cmd 254 55 and it should reply its module type which is 0x0F for the VK204-25 that you have. This of course is an indication that it is indeed ready to communicate.
Please let me know how it turns out.
Raquel Malinis
Design and Development
Matrix Orbital
Design and Development
Matrix Orbital