serial cable supply

#1
I had the usual memory verification issue recently and i found out later that the culprit was the power from my serial adpater cable. The strange part is that it programs my 40x just fine, but none of my 08/08M chips. Has anyone else had this problem when trying to download a program. The strange part is that it can usually see the microchip, so the cable is working somewhat. Also, if i tap the run button quickly, it will download sometimes. Other times it will download and then cut off before the download is finished. Contacts are fine, and the circuit is the normal stuff.
 
#2
What brand etc is the cable and is the power coming 100% from the cable? I either use 3x1.5V or a 9V/78L05 or a 5V supply to power the chip during programming. If the cable is providing the 5V and the supply is collapsing half way through a download, maybe a 470uF cap across the picaxe power supply?
 
#3
im not exactly sure what brand of cable it is, but its your standard serial to stereo. I'll give the capacitor a try, but i don't see why it would collapse half way through on 08/08M's when it will work fine for the 40x?
 
#4
i'm so good at picaxe 08/08M's, that i can make multiple memory verification errors now! take that! 155,127,119,118,116,108..only the most elite can produce such results. :(
 
#5
I'm still a bit unclear about what cable you have, sorry. You say it is the standard serial to stereo. But the stereo plug has no power - it just has ground, Tx and Rx. Where is the power coming from?

Edited by - Dr_Acula on 30/08/2007 05:41:01
 
#6
I'm also confused by your statement "the culprit was the power from my serial adpater cable".
The 'standard' serial cable does NOT supply power.

How ARE you powering the chip?
What voltage?
Does your PC put out +/- 12v or +5v/0v on its serial line.
 

xstamp

Senior Member
#7
I have found that power supply arrangements that otherwise work reliably can cause problems during programming. The measured current draw of the PICAXE at least doubles during programming. However, this is only an average and I expect there are much larger spikes in current demand. The simple way to reduce local voltage drops, due bad pcb layout and power supply wiring resistance, is to connect a 47uF electrolytic and parallel 0.1uF capacitor as near to the PICAXE ground and + supply pins as possible.

 
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