On 9/25/06, Michael Rigby-Jones wrote: > > > >-----Original Message----- > >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] > >Sent: 25 September 2006 14:38 > >To: Microcontroller discussion list - Public. > >Subject: Re: [EE] I need a circuit for a bidirectional opto > >isolated TTLinterface > > > > > >On 9/25/06, Michael Rigby-Jones > > wrote: > >> > >> > >> >-----Original Message----- > >> >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] > >> >Sent: 25 September 2006 11:26 > >> >To: 'PICLIST' > >> >Subject: [EE] I need a circuit for a bidirectional opto > >isolated TTL > >> >interface > >> > > >> > > >> >I was thinking of using HEX inverters and opto isolators that > >> >basically are two unidirectional circuits back to back. > >> > > >> >Works in simulation but do not know how well it will work > >in the real > >> >world :-( > >> > > >> >I want to opto isolate the JTAG programmer interface from the real > >> >world as I may otherwise and with Murphy's Law help blow up my > >> >programmer :-( > >> > >> The first problem is likely to be speed related, common/cheap > >> opto-isolators are v..e..r..y s..l..o..w. > > > > > >6N137 it's a common/cheap one (about $0.6 here if you buy > >one): > >http://www.datasheetcatalog.com/datasheets_pdf/6/N/1/3/6N137.sh > tml > > Still quite slow though. I guess the OP needs to specify what kind of clock speeds his programmer is capable of, but JTAG programmers can have clock speeds in the 10's of MHz range. There are easy solutions for everything if you live in the US: http://www.chipcatalog.com/Datasheet/1B713E67D69216AB53ED9F148DE9424D.htm Please don't ask me about price... Vasile -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist