SVP-324 LCD problem

I just got an SVP-324 controller. The demo program worked fine the first time I powered it up. After the first time that I reprogrammed it (blinking LED) the LCD stopped working. I’ve downloaded the example LCD programs and the demo program but the LCD doesn’t display any characters. When I adjust the contrast pot there isn’t any change on the display. It seems as though the LCD isn’t being initialized. Any ideas?


The blinking LED demo doesn’t use the LCD, so it’s no surprise that it would stop working when programmed with that hex file. Are you sure you used the right hex files when trying to reprogram it with the LCD demos? Note that the AVRISP dialog doesn’t automatically point to the hex file of the program you last compiled; rather, it points to the hex file you last loaded onto an AVR. Is it possible that you’ve just been repeatedly programming it with the blinkLED hex file? Can you get any of the other board behavior to work, such as the buzzer, the motor drivers, a different LED blinking pattern, etc? Also, have you ever removed the LCD?

- Ben

After I programmed the blinking LED program, I then tried one of the LCD example programs but I didn’t get anything on the display. So I then reloaded the demo program. I think that the demo program is working because the when I press the pushbuttons the buzzer beeps and plays a tune and the the LED flashes so I think that it is going through the menus even though nothing is displayed on the LCD. The display worked fine with the demo program before I reprogrammed the controller. I didn’t remove the LCD from the board, but I made sure that it is firmly seated on the connector. The backlight is lit. I tried adjusting the contrast, but there is no change in the display. I can’t see any reason why reprogramming the controller would have any effect on the LCD. Could it just be a coincidence that the display went bad after the first reprogramming?

I think it’s very unlikely for the LCD to randomly fail, and it’s even less likely that such a failure would coincidently occur right after the first reprogramming. Is it possible you changed any of the SVPs fuse bits? Can you look under the Fuses tab of the AVRISP dialog box and read me the fuse byte values you see (the hex values for the bytes are listed near the bottom of the dialog)? If you try the buzzer example programs, do you hear sounds from the buzzer, and if so, do they sound normal? Also, what is the file path of the demo program hex file you’re loading onto the board?

- Ben

The fuse bits are
extended = 0xFC
high = 0xDF
low = 0xE6

I’ve tried all of the example programs that use the buzzer or the leds and they all work fine.

What is the full file path of the demo hex file you are trying to program? I really suspect you might be trying to program with code for the wrong device. Have you verified that the motor drivers are working properly? I’ll have to verify that the fuse bits are correct when I get into work tomorrow?

- Ben

Here is the full path C:\Users\rmh\Desktop\AVRStudio\libpololu-avr-101104\libpololu-avr\examples\atmega324p\hex_files\svp-demo-program.hex . I tried the motors and servo examples but none of them work. Also the buzzer now just pops instead of playing tones. I can still program the leds and change the blink rate. I thought it might be a power issue, but now I’m using a regulated bench supply at 9V but no luck.

Your fuses are correct and that file path looks right. What power supply were you using before the 9V bench supply?

- Ben

Everything is working okay now except the LCD display. The motors, servo, buzzer and leds work with the example programs. I pulled off the LCD display and checked the control lines with a scope. The control signals appear to be correct. I’ll try to wire the LCD to another microcontroller to see if can get anything. Thanks for your help.

What did you do to get them working again? Is there any chance the LCD is now working, too, but the LCD contrast pot is in not set properly?

- Ben

I found a little 2x8 LCD display with the same connector in my parts, plugged it in and it works fine. The only 2x16 LCDs that I have use the single line connectors. I don’t know why the original one just quit working that suddenly.
Thanks for your help.

So just to make sure I understand, when you plug the 8x2 LCD into the SVP, it works? Please contact me directly at ben at pololu dot com and I can get you a replacement LCD.

- Ben