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jgschmidt
Joined: 03 Dec 2008
Posts: 184
Location: Gresham, OR USA
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| PIC16F1825 Data Signal Modulator - UPDATED see below |
 Posted: Tue Apr 16, 2013 5:47 pm |
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Hi,
I need to do some 38KHz carrier IR signalling and was bemoaning the need for another part just to AND the carrier and data. However, I was re-reading the data sheet for the PIC16F1825/1829 part and noticed the Data Signal Modulator (DSM) (Section 23), so perhaps not anymore...
I checked my CCS (PCWHD 4.135) help file and found a DSM section in the functional overviews. However, there is no page in the manual for the referenced setup_dsm() function.
So my questions are:
1) does anyone know where to find the detailed documentation for setup_dsm()?
2) I'm no EE and don't totally understand the data sheet - is the DSM suitable for sending serial data via IR? I'd then like to receive it via a typical 38khz IR receiver connected to the RX pin of another PIC. My hardwired connection works fine but I ultimately can not have a physical connection. My transmission distance is on the order of centimeters.
3) Does anyone who may have done this have any recommendations? (fastest data rate, recommended DSM settings, etc.)
Thanks in advance for any help.
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Jürgen
www.jgscraft.com
Last edited by jgschmidt on Wed Apr 17, 2013 1:46 pm; edited 1 time in total |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Tue Apr 16, 2013 6:09 pm |
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Setup_dsm is covered in the PCD manual, page 63, and includes a pretty
good description of how it works (not as good as the data sheet though).
All the usage is also covered. Looks like OOK might be what you need.
| Quote: | The Data Signal Modulator (DSM) allows the user to mix a digital
data stream (the “modulator signal”) with a carrier signal to produce a
modulated output. Both the carrier and the modulator signals are supplied
to the DSM module, either internally from the output of a peripheral, or
externally through an input pin.
The modulated output signal is generated by performing a logical AND
operation of both the carrier and modulator signals and then it is provided
to the MDOUT pin.
Using this method, the DSM can generate the following types of key modulation schemes:
- Frequency Shift Keying (FSK)
- Phase Shift Keying (PSK)
- On-Off Keying (OOK)
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jgschmidt
Joined: 03 Dec 2008
Posts: 184
Location: Gresham, OR USA
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| Posted: Tue Apr 16, 2013 8:47 pm |
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Thanks, that helps a little.
Looks like I'm out of luck, however, because I get "Unidentified identifier -- setup_dsm" when I try to use the function with the 16F1825.
When I check the Devices files there are 6 24FJxGAx devices that have DSM_ entries.
Sigh!
In my searching I came across the following:
http://www.rentron.com/Micro-Bot/IR_Serial.htm
which is a pretty sneaky solution! I'll give that a try.
Cheers,
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Jürgen
www.jgscraft.com |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Setup_dsm() |
| Posted: Tue Apr 16, 2013 9:01 pm |
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You don't have to use the setup_dsm(). You can access the registers
directly. It looks pretty straightforward. If I had one of them I would
give it a shot. I'll get one on order to play with.
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jgschmidt
Joined: 03 Dec 2008
Posts: 184
Location: Gresham, OR USA
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| Posted: Wed Apr 17, 2013 8:43 am |
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Oops! Duh! Forgot about that. Thanks for the reminder. I'll set up my #bytes and #bits and see how it goes.
Cheers,
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Jürgen
www.jgscraft.com |
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jgschmidt
Joined: 03 Dec 2008
Posts: 184
Location: Gresham, OR USA
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| Posted: Wed Apr 17, 2013 1:52 pm |
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For anyone interested here is some sample code that successfully demonstrates the Data Signal Modulator ( DSM ) of the PIC16F1825.
| Code: |
#case
// 1825DSMTest.c Data Signal Modulation Test
//
// 16F1825/1829
// - All ports support internal weak pullups
// - 25mA sink/source on I/O pins
//
// Target:
// Hardware:
// Compiler: CCS PCWH 4.135
// Programmer: PICkit2
// Dependencies: None
//
// 2013.04.17 - Jurgen G Schmidt www.jgscraft.com
//
// + VDD - 1 14 - VSS -
// OSC1/RA5 - 2 13 - RA0/DAT
// OSC2/RA4 - 3 12 - RA1/CLK
// MCLR/RA3 - 4 11 - RA2/CCP3
// CCP1/RC5 - 5 10 - RC0/SCL/SCK
// TX/RC4 - 6 9 - RC1/SDA/SDI/CCP4
// CCP2/RC3 - 7 8 - RC2/ SDO
//
//-----------------------------------------------------------------------------
#include <16f1825.h>
#FUSES INTRC_IO //Internal RC Osc, no output
#FUSES NOWDT //No Watch Dog Timer
#FUSES NOPUT //No Power Up Timer
#FUSES NOMCLR //Engages weak pullup
#FUSES NOBROWNOUT //No brownout reset
//#FUSES CLKOUT //Check FOSC/4 on pin 3 - should be .125us
#use delay(internal=32M)
//-----------------------------------------------------------------------------
//------ DSM Register Definitions
#byte MDCON = 0x39C //--Modulation control register--
#bit MDEN = MDCON.7 // DSM Enable 1=on
#bit MDOE = MDCON.6 // MDOUT Pin enable 1=on
#bit MDSLR = MDCON.5 // slew rate limiting enabled 1=on
#bit MDOPOL = MDCON.4 // output polarity 1=signal is inverted
#bit MDOUT = MDCON.3 // current value of MDOUT pin
#bit MDBIT = MDCON.0 // 1= Modulator uses high carrier source
#byte MDSRC = 0x39D //--Modulation source control register--
#bit MDMSODIS = MDSRC.7 // 1= disable output signal driving peripheral out pin
#bit MDMS3 = MDSRC.3 // Modulation source
#bit MDMS2 = MDSRC.2 // 0000 = MDBIT of MDCON
#bit MDMS1 = MDSRC.1 // 0001 = MDMIN port pin
#bit MDMS0 = MDSRC.0 // 1010 = EUSART TX output
#byte MDCARH = 0x39F //--Modulation high carrier control register--
#bit MDCHODIS = MDCARH.7 // 1= disable output signal driving peripheral out pin
#bit MDCHPOL = MDCARH.6 // output polarity 1=signal is inverted
#bit MDCHSYNC = MDCARH.5 // Modulator high carrier synchronization 1=on
#bit MDCH3 = MDCARH.3 // Data high carrier selection bits
#bit MDCH2 = MDCARH.2 // 0000 = Vss
#bit MDCH1 = MDCARH.1 // 0100 = CCP1
#bit MDCH0 = MDCARH.0 // 0001 = MDCIN1 port pin (C2 / pin 8)
// set to: 10100100
#byte MDCARL = 0x39E //--Modulation low carrier control register--
#bit MDCLODIS = MDCARL.7 // 1= disable output signal driving peripheral out pin
#bit MDCLPOL = MDCARL.6 // output polarity 1=signal is inverted
#bit MDCLSYNC = MDCARL.5 // Modulator low carrier synchronization 1=on
#bit MDCL3 = MDCARL.3 // Data low carrier selection bits
#bit MDCL2 = MDCARL.2 // 0000 = Vss
#bit MDCL1 = MDCARL.1 // 0100 = CCP1
#bit MDCL0 = MDCARL.0 // 0001 = MDCIN1 port pin (C2 / pin 8)
// set to: 0b10100000
// Test 1 - use MDMIN pin (pin 7) to toggle carrier output on MDOUT (pin 6) WORKS!!!!!
//
// MDCON = 0b11000001; // DSM enable, MDOUT enable, no slew, not inverted, modulator uses high carrier source
// MDSRC = 0b10000001; // disable peripheral, data from MDMIN pin (so we can see triggering on OSCOPE)
// MDCARH = 0b10100100; // disable peripheral, not inverted, synced, data high = CCP1 (38khz carrier)
// MDCARL = 0b10100000; // disable peripheral, not inverted, synced, data low = Vss
//
//-----------------------------------------------------------------------------
void main()
{
setup_adc_ports( NO_ANALOGS);
setup_timer_2(T2_DIV_BY_1, 210, 1 );
setup_ccp1( CCP_PWM );
set_pwm1_duty( 422L ); // 38khz square wave output - 50% duty
MDCON = 0b11000001; // DSM enable, MDOUT enable, no slew, not inverted, modulator uses high carrier source
MDSRC = 0b10000001; // disable peripheral, data from MDMIN pin (so we can see triggering on OSCOPE)
MDCARH = 0b10100100; // disable peripheral, not inverted, synced, data high = CCP1 (38khz carrier)
MDCARL = 0b10100000; // disable peripheral, not inverted, synced, data low = Vss
//------ Big Loop ------
while( TRUE )
{
delay_ms( 1 );
output_toggle( PIN_C0 ); // generate signal for oscilloscope to measure loop time
}//------ end of big loop
}
//-----------------------------------------------------------------------------
//------ end of 1825DSMTest.c ------ |
Happy coding!
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Jürgen
www.jgscraft.com |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Wed Apr 17, 2013 3:41 pm |
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Outstanding! Great job!
How about adding a version of this to the code library?
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jgschmidt
Joined: 03 Dec 2008
Posts: 184
Location: Gresham, OR USA
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| Posted: Wed Apr 17, 2013 5:05 pm |
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I intend to. I want to verify some of the other features, particularly the UART connection. Coming soon...
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Jürgen
www.jgscraft.com |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Sat Apr 20, 2013 4:03 pm |
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JGScmidt,
CCS support just replied with the following:
| Quote: | We currently only have built-in functions for the DSM module in the
PCD compiler. We are planning on adding support for it to the PCM and PCH
compiler in the next few weeks.
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Sun Apr 21, 2013 9:12 am |
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now ifMicrochip had a data DEMODULATOR integrated for NRZ signals
THAT would be a real accompishment
and lots of cheap 433 mhz data connect systems could be better supported too |
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jgschmidt
Joined: 03 Dec 2008
Posts: 184
Location: Gresham, OR USA
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| Posted: Fri Apr 26, 2013 8:30 pm |
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Thanks, dyeatman, for finding that. Working with the CCS compiler for 15 years I know how quickly that can actually happen.
IR send/receive code using the DSM has been posted in the library.
I'd like to know what other chips have the DSM but unfortunately Microchip does not list this feature in their part finder. (Sigh)
My thanks to anyone who adds part numbers having the DSM to this post.
Cheers,
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Jürgen
www.jgscraft.com |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Apr 26, 2013 8:44 pm |
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Do a Google search for this:
| Quote: | | site:microchip.com -forums "data signal modulator" "data sheet" type:pdf |
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jgschmidt
Joined: 03 Dec 2008
Posts: 184
Location: Gresham, OR USA
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| PICs with DSM (Data Signal Modulator) |
| Posted: Sat Apr 27, 2013 10:16 am |
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Thanks. That added one more to the list, which now stands at:
12F18xx and 16F18xx
18LFxxK80
18F97J94 family
24FJ64/128GA306/308/310 <- supported by PCD 4.135
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Jürgen
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Gabriel
Joined: 03 Aug 2009
Posts: 1067
Location: Panama
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| Posted: Tue Apr 30, 2013 7:28 am |
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I was having the same problem of having to add an extra part....
i never got to test my solution, but i thought of using the comparator module as an AND gate.....
you would still need a few resistors but thats easier than adding a whole 14 pin AND gate chip or transistors...
.. i know its late in the thread but someone might find it useful...
G.
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CCS PCM 5.078 & CCS PCH 5.093 |
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