| ??? 04/27/07 00:18 Modified: 04/27/07 00:32 Read: times |
#138068 - all the story! Responding to: ???'s previous message |
Erik Malund said:
why a switch ? It will give you all kins of problems, just replace the crystal in the socket. I do not recall that the ED2 has an oscillator that will run without a crystal. Erik Yes ED2s need external crystal and I have a good one on my board; a 11.0592 which is always there!... why a switch ...because when I don't want to use 11.0592 I want to switch to the other frequency which I gain from an optional crystal that I have placed into the socket.I think pictures help... But Russ,Erik,Richard what made you have such dissaproving look at that poor little switch? why do you offer to replace it with pin header and jumpers? Richard Erlacher said:
it may affect loading of the crystal, so you may have to adjust the cap values used in your oscillator,
............................................................ The shorting plugs take the unused crystal out of the circuit entirely, so it has no effect on the characteristics of the oscillator when not in use. RE Richard you make me worry ,what may affect loading of crystal ?the switch or the idea probably?...what you have suggested is what I have down ,,there is only one crystal in the circuit .pictures may depict what I want to say. But why I'm bothering you ?...mental disorder???! No ,at least not at this case ;-) ...it's a few month that I have designed this board and guys at our company use it . I clearlly remeber that I did a few test and I remeber I were switching between to frequency to gain proper result for example USART in sysytem programming of ED2 with 11.0592 ,but the code needs another frequency to work properly .unforunatly there are weeks that I'm far from that old friend ,8051, in fact I'm forgetting smell of soldering ...few days ago my colleague insisted that this board has desytroyed his timing and when he cut tracks and shorted them like a simple single crystal connection ,it worked correctlly !!.. I don't have needed parts around myself these days to test it,I guessed maybe there is something about crystals or oscillator that I don't know,according to my information it is impossible ,what do you think??? I will test it in following days ,such visible error that he declared can be tested easilly ,I know it is my duty ,in fact I didn't want to prolong this thread like this.I just want to check if anyone had experienced this idea or know any point that is unclear for me... if it was not as bad as my collegue said, can I trust compeletly to this board? ...is it different to switch XTAL1 pin instead of XTAL2...do you find stray capacities considerable here?I don't! Koosha 
red arrow shows the switch , and blue one the crystal socket which in not a real one , a 3pin female header which it's middle pin has no connection.look at that cheap chinese ZIF ;-)) 
schematic ! 
PCB! |
