TV Display problems
Levitis Leviathan
Posts: 32
When I first wired up by Propeller breadboard system, I was able to get the display.spin program to run correctly. Now that I am going through the examples in the book step by step, I cannot get ANY output on the TV. I've tried several tv's and patch cables with the same results. I am using the 5 mHz external crystal. I have double checked that no wires are loose or misconnected, and have even verified the resistor values with a multimeter. Are there any others having similar problems? Are there any voltages which should be present at the chip output pins to verify that it's not a bad chip videowise?
Comments
if all that is ok.. you could try to run 2 cogs with a blinking led in each to check the chip.... I went and accidentally put 10v to a pin and after that i could not get more than one cog to run ( which you need for the tv-display ) the chip would still blink bunches of leds, but i could not get it to run more than one cog..
dan
I thought about the power supply issues, since when I had initial success with tv output I was using 3.75 vdc from three AA batteries. I tried the battery route again without success.
I'm going to replace the resistors and associated wiring to the rca connector tomorrow.
http://forums.parallax.com/forums/default.aspx?f=25&m=136976&g=137109#m137109
Also have you tried running blinker.spin at 80mhz to make sure it is working at that speed?
I read the thread referenced, and I do have a 1 uF cap across Vss and Vdd in conjunction with the LM317T voltage regulator on the breadboard, so the chip isn't being powered by the wall wart alone.
I tried the blinker.spin program and it does NOT work with the xtal1 + pll16x code, though it runs with xtal1 + pll4x and 8x (very much like the problem you raised in the thread.) However, if I run the same program without this line of code, the leds all blink at the apprpriately rapid rate.
Are you suggesting the 10 uF be subbed for the 1 uF across Vss and Vdd?
Thank for your for assistance with this tricky problem. I'm wondering if the 5.0 MHz xtal didn't go bad...
If your wall wart is filtered, put a 0.1uF cap on the input side of the LM317. If it's not filtered (e.g. designed for a battery charger), 1000uF on the '317's input wouldn't be too much. (You can tell whether it's filtered or not by looking at the wall wart's output on a scope. If it's smooth with a slight 120Hz ripple, it's filtered. If the voltage goes to zero periodically, it's not filtered.)
-Phil