Reply by Martin Griffith 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
Reply by TheM 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 > > martin
A 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 Martin Griffith 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 TheM 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 > > martin
One question, is it a problem if your data stream is audible? M
Reply by Frank Buss 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
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 lang...@fonz.dk 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 RFI-EMI-GUY October 6, 20082008-10-06
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"&#4294967295; "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P
Reply by lang...@fonz.dk October 6, 20082008-10-06
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
Reply by whit3rd October 6, 20082008-10-06
On Oct 4, 1:26=A0pm, 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
Usually, to AC couple serial data, like 'through a transformer', one uses a modem. Apple's old Appletalk used a Zilog 8530 SCC (serial communication controller) feature, the "FM1" mode, to make a good signal connection through transformer coupling, and lots of high-end SCC chips, with suitable differential transceivers, can do the same. This is a step up from a UART, but it's do-able in software. That old 8530 chip, with a (?4) MHz clock, could run two channels at about 230 kbaud in FM1 mode; the old Macintosh could only keep up with the data from one, and that required full participation of the OS (i.e. a kernel-resident driver). Modes like FM1 that might be in a USART implementation include MFM, FM, FM1, FM2, RLL, X.25, etc... The higher the frequency, the smaller/cheaper the transformer. Transmitter chips 26LS30, receivers 26LS32 or SN75175 are suitable. One sees this kind of trick in floppy and hard disk drives, too (and some of those same drivers in disk controllers), because the same issue arises in serial-to-magnetic media that you have in serial-to-transformer coupling.