Propeller first turn on problems
stoveitin
Posts: 11
Hello,
I have got a P8X32A-D40 running on a simple stripboard set up to test some features using a AT24C512C for the EEPROM.
It programs and runs okay.
But when you first turn it on fresh power up and it loads the code from EEPROM it doesn't allways run the code and have to start it with a manual reset by pulling the reset low.
I have watched the reset line with a scope and its nice and steady on power up.
All I can find is that the data line too the EEPROM looks very spikey and no nice square data on and off bits like there is with the clock line but this maybe normal.. unsure. Also on the times it does not run the code the EEPROM data chatting is much shorter compared to when the code fires up.
Any ideas ?
The reset line runs into the collector of a BC337 NPN been pulled down via that for programing .
Cheers for your time.
I have got a P8X32A-D40 running on a simple stripboard set up to test some features using a AT24C512C for the EEPROM.
It programs and runs okay.
But when you first turn it on fresh power up and it loads the code from EEPROM it doesn't allways run the code and have to start it with a manual reset by pulling the reset low.
I have watched the reset line with a scope and its nice and steady on power up.
All I can find is that the data line too the EEPROM looks very spikey and no nice square data on and off bits like there is with the clock line but this maybe normal.. unsure. Also on the times it does not run the code the EEPROM data chatting is much shorter compared to when the code fires up.
Any ideas ?
The reset line runs into the collector of a BC337 NPN been pulled down via that for programing .
Cheers for your time.
Comments
Note Clock 1v Data 500mv
Send us a picture of your setup.
1. I suspect you don't have enough capacitance on the power buses.
2. All VDD[\sub] and VCC[\sub] pins must be connected. On plugboards it is easy to add a pair of jumpers under the chip to cross couple the pairs of VDD[\sub] and VCC[\sub] pins.
3. Make sure you have at least a 10K pullup on the SCL and SDA lines to the memory/
4. Make sure the address and chip select pins are appropriately tied HI or LOW.
Duane J
Duane J
Incoming 5volts to ceramic 0.1uf cap into 3.3 volt reg then polarized 10uf cap.
EEPROM has no cap next to it slaved a 0.1uf in few hours go next to it seemed to not effect it I could attach one properly if recommended.
Cheers Tom.
-Phil
The 0.1uF ceramic cap you are using is not the recommended one for decoupling - you need a monolithic X7R preferred. They are the colored variety (often blue).
You could also try using a tantalum 10uF capacitor as well.
Normally, none of the above would be absolutely necessary for just testing, but you have problems somewhere, and these are the things that can cause problems.
The other area is your RS232 to TTL converter. Perhaps you could post a diagram of it and some pics too. Also post a pic of the underside of your pcb. The more info we have the more help we can offer.
Found its something to do with the clock and crystal.
when I probe the crystal it works every time and stops working soon as I don't probe it .
Suspect the capacitance in the oscilloscope probe has something to do with it.
How come this microcontroller needs no caps on the crystal guess there internal.
I have found the crystal in the metal can has fairly small lead diameter.
I like to put a small "Crimp" in the crystal lead so the machined socket can effectively grip the lead.
Duane J