📄 dc-rx.htm
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<H2>General coverage receiver 0-50Mhz (ULF to HF/VHF)<BR>based on AD9854 DDS
direct digital synthesis chip<BR>
<HR noShade SIZE=1>
</H2><U><FONT size=4>Overview</FONT></U><BR><BR>This is basically a direct
conversion receiver. The LO frequency synthesis is based on the AD9854 DDS chip
(I/Q quadrature direct digital synthesis, visit <A
href="http://www.analog.com/">http://www.analog.com/</A> for the datasheet and
sample orders).<BR><BR>There are two detectors: one is a conventional AD831
mixer based downconversion board, the other is a Tayloe detector i.e. an N-path
sampling filter (<A
href="http://www.flex-radio.com/">http://www.flex-radio.com/</A>, see SDR
Articles section). An upwards sampling system as in the 4th SDR paper could be
used for the transmitter section.<BR><BR>The DDS is programmed and controlled by
a MSP430F149 microcontroller (MSP430 series, 60kB flash, 256B ram, 48 I/O pins).
Peripherals of the DC-RX system include: a 2-line LCD, a standard PC keyboard, a
PC RS-232 cable for remote control, and an inexpensive DIY <A
href="http://users.tkk.fi/~jwagner/electr/rotary-enc/">tuning
wheel</A>.<BR><BR>The mainboard contains all user interface and DDS related
parts and may be used for other purposes too, t.ex. as a LO for another rx/tx or
for phase modulation, chirping, keying, and using other features of
AD9854.<BR><BR><BR>
<TABLE width="100%" border=0>
<TBODY>
<TR>
<TD vAlign=top width="50%"><U><FONT size=4>Dev tools</FONT></U><BR><BR>All
software tools are freeware or GPL.<BR><BR>Schematics and PCB layout: <A
href="http://www.cadsoft.de/">Eagle</A> (english and german, Linux +
Windows)<BR><BR>MSP430 firmware upload and debug: <A
href="http://www.noicedebugger.com/">NoICE remote debugger</A><BR><BR>JTAG
programming adapter: <A
href="http://www.olimex.com/dev/msp-jtag.html">Olimex MSP430-jtag</A> for
schematics. I built it without the TPS77030 and MCP601, as the uC &
DDS boards draw way too much current (500mA..1A) to be supplied by the PC
parallel port.<BR><BR>C/C++ compiler: <A
href="http://mspgcc.sourceforge.net/">msp430-gcc</A> gnu c toolchain for
MSP430 (best compiler for this purpose, but no graphic IDE), IAR MSP430
tools from <A href="http://www.ti.com/msp430">Texas Instruments</A> (4kB
limit!), or <A href="http://www.ide430.com/">IDE430</A><BR><BR><BR></TD>
<TD vAlign=top width="50%"><U><FONT size=4>Libraries</FONT></U><BR><BR><A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/analog-devices-dds.lbr">analog-devices-dds.lbr</A>
: <B>AD9854</B> library file for Eagle. Additionally contains the classic
<B>AD831</B> low distortion high IP3 doubly-balanced mixer<BR><BR><A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/texas-msp.lbr">texas-msp.lbr</A>
: <B>MSP430F149</B> library file for Eagle (same pin-out for
MSP430F147/148/149). Additionally contains the <B>MAX3221</B> ultra low
standby current RS-232 driver/receiver, <B>INA163</B> low noise low
distortion instrumental amplifier, <B>TL714</B> open drain fast 50MHz
analog comparator, and <B>TPS75833</B> 3.3V 3A lo-drop fast transient
response regulator.<BR><BR></TD></TR>
<TR>
<TD vAlign=top width="50%"><U><FONT size=4>Schematics</FONT></U><BR><BR>
<UL>
<LI>mainboard with uC and DDS<BR><SMALL>fully working final design, LCD
and PC keyboard optional, main control via RS232 and the tuning wheel.
The PCB has been cleaned up a bit now (10/04/04).</SMALL><BR><BR>Eagle
[<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/msp430-uC-9854-combo.sch">sch</A>]
[<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/msp430-uC-9854-combo.brd">brd</A>]<BR>GIF
[<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/mb-sch.gif">schematic</A>]
[<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/mb-top-bot.gif">PCB</A>]
[<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/mb-top-pts.gif">top
parts</A>] [<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/mb-bot-pts.gif">bot
parts</A>]<BR>and <A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/pics/mainboard.jpg">photo
1</A>, <A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/pics/uC_DDS_combo.jpg">photo
2</A> (heatsink solution)<BR><BR><U>update:</U> <A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/work/msp430-DDSboard.zip">new
Eagle files</A> for a slightly updated board (LCD connector, external 5V
supply, JTAG with TSTCLK signal, connectors rearranged a bit)
<BR><U>info update:</U> 08/2005, Barry KK4VT pointed out an error in the
AT keyboard pins, on the brd and sch the keyboard should go to P2.6 and
P2.7 instead of P2.5 and P2.6 - I'll try to update the firmware soon.
Second, FIN1028 doesn't put out 50% duty squarewaves, probably because
DDS output resistors and filter double-termination should be as in
flex-radio article 4, or then some other better solution. Working on
it...<BR><BR>
<LI>AD831-based analog mixer<BR><SMALL>non-optimal prototype, mixer
appears to be overdriven somehow, reception quality reminds of rain
barrel sound...</SMALL><BR><BR>Eagle [<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/msp430-scanner-RFmixer.sch">sch</A>]
[<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/msp430-scanner-RFmixer.brd">brd</A>]<BR><BR>
<LI>"digital" downsampling Tayloe mixer v1.5<BR><SMALL>Works nicely. The
sch and PCB have been updated and cleaned. The center-tapped 1:1:1
transformer ('isolated balun') requires a proper RF ferrite, small
Amidon balun cores will do just fine. The board output needs about +40dB
AF (e.g. PC soundcard microphone input). Features alternative inputs:
I/Q LVDS >200mV, I/Q LVTTL 3.3V, single TTL 5V
(2<SMALL>x</SMALL>f<SUB>RX</SUB>). Unused input components can be
omitted.<BR><U>Note:</U> there's a problem with the INA163's. Sometimes
they switch to massively attenuate the input difference signal, though
signals and voltages on all pins would suggest it <I>should</I> still be
giving x50.000 gain - working to debug the problem... (July 17 /
04)</SMALL><BR><BR>Eagle [<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/msp430-scanner-TayloeMixer-v15.sch">sch</A>]
[<A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/schematics/msp430-scanner-TayloeMixer-v15.brd">brd</A>]<BR><BR></LI></UL></TD>
<TD vAlign=top width="50%"><U><FONT size=4>Other files</FONT></U><BR><BR>
<UL>
<LI><A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/firmware/"><B>mainboard
firmware v1.0</B></A><BR>runs on the MSP430F149, preprogrammed for a 50
MHz crystal osc as the DDS ref_clk input (can be changed in
MSP430-fw-dds.h)<BR><BR>
<LI><A href="http://users.tkk.fi/~jwagner/electr/dc-rx/pics/">new and
old photos</A><BR>
<LI><A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/cheddar54-source/">VisualBasic
source code for PC software</A><BR>(not very complete...)<BR>
<LI>audio samples (added later)<BR>
<LI>DRM <A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/recordings/">recordings</A><BR>(for
now, just Dream DRM rx log of 30.05.2005 tests)<BR></LI></UL><U><FONT
size=4>Parts</FONT></U><BR><BR>All semiconductor parts used in the
mainboard are available as free samples, or can be bought from DigiKey and
others.<BR><BR><SMALL>Free samples:<BR><A
href="http://www.analog.com/">Analog Devices</A>: AD9854 AD831<BR><A
href="http://www.fairchildsemi.com/">Fairchild</A>: FIN1028 FSAV331<BR><A
href="http://www.ti.com/">Texas Instruments</A>: MSP430F149 MAX3221
TPS75833 CD74HC573M<BR></SMALL></TD></TR>
<TR>
<TD><U><FONT size=4>Notes:</FONT></U><BR><BR>The RS232 serial port on the
uC/9851 board is set to 9600 baud, 8 data, 1 stop, no parity, no flow
control. Also, the MAX3221 has an autoshutdown feature, meaning that if it
doesn't find a valid RS232 voltage level on the DB9 connector RX/TX lines
for some time, it will shut down. So, before trying to debug serial comm,
connect the cable to a PC - otherwise you might be surprised to find no
output.<BR><BR>Because many people have asked, I've now added a page with
some infos on <A
href="http://users.tkk.fi/~jwagner/electr/dc-rx/PCB_devel.htm">how to make
etched SMD PCB boards</A> with standard equipment.<BR><BR></TD>
<TD></TD></TR></TBODY></TABLE><BR>
<P></P>
<P><BR></P>
<P>
<HR noShade SIZE=1>
(C) 2003 Jan Florian Wagner, OH2GHR<BR>jwagner at cc hut fi<BR><BR>
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