langwadt@fonz.dk wrote:> On 6 Okt., 00:50, "Tam" <t-tamm...@comcast.net> wrote: >> "MooseFET" <kensm...@rahul.net> wrote in message >> >> news:32fda7c9-35ea-4d94-a64f-6c2f2955d5e7@i24g2000prf.googlegroups.com... >> On Oct 4, 1:26 pm, Martin Griffith <mart_in_med...@yah00.es> wrote: >> >>> Any rules of thumb about sending a 9600 baud UARTsignal ,from an 8051 >>> through a telecom type V90 audio transformer, (LT spice K L1 L2 1 @ >>> 4mH Rs = 10R) >>> I only need about 8 bytes of data, and LTspice seems to need a square >>> wave for about a millisecond before it settles down. >>> So a long sync word of 010101 etc then a start byte? >>> I'll pad the sig down to 100mV or so >> The DC offset needs to be handled. >> >> (1) you can duck the whole issue: >> The simplest way to do this is to use "glitch code modulation". Run >> the RS-232 through a high pass filter so that it is only spikes on the >> edges. > snip > > Thats kinda how the IrDa works, ones are no light, zeros > is a 3/16 or 4/16 bit "blink" > > -Lasse > > > > >Why not Manchester coding? -- Joe Leikhim K4SAT "The RFI-EMI-GUY"� "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P
Uart through an audio transformer
Started by ●October 4, 2008
Reply by ●October 6, 20082008-10-06
Reply by ●October 6, 20082008-10-06
On 7 Okt., 03:52, RFI-EMI-GUY <Rhyol...@NETTALLY.COM> wrote:> langw...@fonz.dk wrote: > > On 6 Okt., 00:50, "Tam" <t-tamm...@comcast.net> wrote: > >> "MooseFET" <kensm...@rahul.net> wrote in message > > >>news:32fda7c9-35ea-4d94-a64f-6c2f2955d5e7@i24g2000prf.googlegroups.com... > >> On Oct 4, 1:26 pm, Martin Griffith <mart_in_med...@yah00.es> wrote: > > >>> Any rules of thumb about sending a 9600 baud UARTsignal ,from an 8051 > >>> through a telecom type V90 audio transformer, (LT spice K L1 L2 1 @ > >>> 4mH Rs = 10R) > >>> I only need about 8 bytes of data, and LTspice seems to need a square > >>> wave for about a millisecond before it settles down. > >>> So a long sync word of 010101 etc then a start byte? > >>> I'll pad the sig down to 100mV or so > >> The DC offset needs to be handled. > > >> (1) you can duck the whole issue: > >> The simplest way to do this is to use "glitch code modulation". Run > >> the RS-232 through a high pass filter so that it is only spikes on the > >> edges. > > snip > > > Thats kinda how the IrDa works, ones are no light, zeros > > is a 3/16 or 4/16 bit "blink" > > > -Lasse > > Why not Manchester coding? >for IrDa? one is the idle state of a uart, making that no light saves power -Lasse
Reply by ●October 7, 20082008-10-07
On Oct 4, 2:01=A0pm, Frank Buss <f...@frank-buss.de> wrote:> Tam wrote: > > Are you trying to send a signal that has a DC level associated with it,=like> > straight binary data? =A0Capacitive coupling won't help either. You nee=d to> > encode the signal so that there is net 0 DC on it. > > And one solution would be to use biphase encoding: > > http://en.wikipedia.org/wiki/Biphase_mark_code > > Or Manchester code, like used for Ethernet. > > -- > Frank Buss, f...@frank-buss.dehttp://www.frank-buss.de,http://www.it4-sys=tems.de Or Modified Duobinary. My recollection is not only does it get rid of DC, but it has a less low frequency content. I took a pulse modulation class from Adam Lender in the dark ages. To say he was demanding puts it kindly.
Reply by ●October 7, 20082008-10-07
miso@sushi.com wrote:> Or Modified Duobinary. My recollection is not only does it get rid of > DC, but it has a less low frequency content.How does it look like? I've found this for Duobinary: http://www.knowledgerush.com/kr/encyclopedia/Duobinary_signal/ Looks like you'll need an additional clock signal for it or some other synchronisation, like the start/stop bit in RS232. -- Frank Buss, fb@frank-buss.de http://www.frank-buss.de, http://www.it4-systems.de
Reply by ●October 7, 20082008-10-07
"Martin Griffith" <mart_in_medina@yah00.es> wrote in message news:j8jfe4d1mv1qgb3bhmf10fqr8ltnuotrhm@4ax.com...> Any rules of thumb about sending a 9600 baud UARTsignal ,from an 8051 > through a telecom type V90 audio transformer, (LT spice K L1 L2 1 @ > 4mH Rs = 10R) > I only need about 8 bytes of data, and LTspice seems to need a square > wave for about a millisecond before it settles down. > So a long sync word of 010101 etc then a start byte? > I'll pad the sig down to 100mV or so > > martinOne question, is it a problem if your data stream is audible? M
Reply by ●October 7, 20082008-10-07
On Tue, 7 Oct 2008 15:39:20 +0200, in sci.electronics.design "TheM" <DontNeedSpam@test.com> wrote:> >"Martin Griffith" <mart_in_medina@yah00.es> wrote in message news:j8jfe4d1mv1qgb3bhmf10fqr8ltnuotrhm@4ax.com... >> Any rules of thumb about sending a 9600 baud UARTsignal ,from an 8051 >> through a telecom type V90 audio transformer, (LT spice K L1 L2 1 @ >> 4mH Rs = 10R) >> I only need about 8 bytes of data, and LTspice seems to need a square >> wave for about a millisecond before it settles down. >> So a long sync word of 010101 etc then a start byte? >> I'll pad the sig down to 100mV or so >> >> martin > >One question, is it a problem if your data stream is audible? > >M >Hopefully, it's to timestamp, in a very primitive way an audio feed. The idea is to just dump N81, from the uart at a low level, say -30 or-40dBFS, and then have a little black box containing a preamp to logic levels to drive a FTDI 232/USB thing, or maybe a USB HID/ keyboard. I like the idea of using a cheapo telecom/modem transformer, because it is floating, and will take up less PCB real estate than the electronically balanced equivalent. The Etal P3181 ( from farnell etc) seems to fit the requirements I'll try it on my canon xl1s audio channels, to see if it works, when I get my hands on a P3181 martin
Reply by ●October 7, 20082008-10-07
"Martin Griffith" <mart_in_medina@yah00.es> wrote in message news:b0rme4lm0vsc3s5ng39n7e3iiglqjg0qq2@4ax.com...> On Tue, 7 Oct 2008 15:39:20 +0200, in sci.electronics.design "TheM" > <DontNeedSpam@test.com> wrote: > >> >>"Martin Griffith" <mart_in_medina@yah00.es> wrote in message news:j8jfe4d1mv1qgb3bhmf10fqr8ltnuotrhm@4ax.com... >>> Any rules of thumb about sending a 9600 baud UARTsignal ,from an 8051 >>> through a telecom type V90 audio transformer, (LT spice K L1 L2 1 @ >>> 4mH Rs = 10R) >>> I only need about 8 bytes of data, and LTspice seems to need a square >>> wave for about a millisecond before it settles down. >>> So a long sync word of 010101 etc then a start byte? >>> I'll pad the sig down to 100mV or so >>> >>> martin >> >>One question, is it a problem if your data stream is audible? >> >>M >> > Hopefully, it's to timestamp, in a very primitive way an audio feed. > The idea is to just dump N81, from the uart at a low level, say -30 > or-40dBFS, and then have a little black box containing a preamp to > logic levels to drive a FTDI 232/USB thing, or maybe a USB HID/ > keyboard. I like the idea of using a cheapo telecom/modem transformer, > because it is floating, and will take up less PCB real estate than the > electronically balanced equivalent. > The Etal P3181 ( from farnell etc) seems to fit the requirements > > I'll try it on my canon xl1s audio channels, to see if it works, when > I get my hands on a P3181 > > martinA bit steep, but a nice no-hassle part. I wonder how it performs above 4KHz. I was recently thinking about sending some data over audio channel, but above audible range. Haven't quite figured out yet how to do it without much hardware. FSK at 20+ KHz probably. M
Reply by ●October 7, 20082008-10-07
On Tue, 7 Oct 2008 15:39:20 +0200, in sci.electronics.design "TheM" <DontNeedSpam@test.com> wrote:> >"Martin Griffith" <mart_in_medina@yah00.es> wrote in message news:j8jfe4d1mv1qgb3bhmf10fqr8ltnuotrhm@4ax.com... >> Any rules of thumb about sending a 9600 baud UARTsignal ,from an 8051 >> through a telecom type V90 audio transformer, (LT spice K L1 L2 1 @ >> 4mH Rs = 10R) >> I only need about 8 bytes of data, and LTspice seems to need a square >> wave for about a millisecond before it settles down. >> So a long sync word of 010101 etc then a start byte? >> I'll pad the sig down to 100mV or so >> >> martin > >One question, is it a problem if your data stream is audible? > >M >Not a problem, the data is only dumped when required. been mucking around with some irritating 8051 bugs, so I havent really got any further with this martin
