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Discussion Groups | Freescale DSPs | where to start
Technical discussions about Freescale (Motorola) DSPs (including the DSP56000, DSP56300, DSP56600, 56800 DSPs).
where to start - Jacques Malan - Jan 5 5:12:00 2000
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Hi there, I am a newcomer in the DSP world and would appreciate some guidance as to where to start. I have designed a 4Kbit oqpsk analogue receiver and would like to implement it in a DSP. I have a DSP5603 development kit working at a 100Mhz. What I think I should do next is to take each building block of the design i.e. a mixer a Low Pass filter,VCO etc. and some how determine how many clockcycles each component will need and whether I will be able to fit it into the 5603 DSP. Is there example code for these types of parts VCO etc. I have experience in C programming but have never done a DIGITAL demodulation design let alone on a DSP. I would appreciate ANY suggestions and guidance Thanks Jacques ______________________________________________________ |
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Re: where to start - Crazy Baby - Jan 5 15:26:00 2000
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hi there.. Likewise, I am a newcomer to DSP and most of my knowledge of DSP is theoretical. So unfortunately I wont be much help. Good luck ______________________________________________________ |
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Re: where to start - Bharat Meshwani - Jan 5 16:43:00 2000
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Hello, Check out the Motorola DSP web site. They have all the tools and some example code for all the DSPs. The DSP evaluation kit also comes with an example source code. Also try sending help request to Motorola DSP web site. Most of the time C programming works. You can stay away from assembly, like I do as much as possible. The rest comes with experience and learning. It is a slow process. Good luck Bharat Meshwani Jacques Malan wrote: > Hi there, > I am a newcomer in the DSP world and would appreciate some guidance as to > where to start. > > I have designed a 4Kbit oqpsk analogue receiver and would like to implement > it in a DSP. > I have a DSP5603 development kit working at a 100Mhz. > > What I think I should do next is to take each building block of the design > i.e. a mixer a Low Pass filter,VCO etc. and some how determine how many > clockcycles each component will need and whether I will be able to fit it > into the 5603 DSP. Is there example code for these types of parts VCO etc. > I have experience in C programming but have never done a DIGITAL > demodulation design let alone on a DSP. > > I would appreciate ANY suggestions and guidance > > Thanks > Jacques > > ______________________________________________________ > > | |||||||
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Re: where to start - Stéphane Cnockaert - Jan 5 19:08:00 2000
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Dear Jacques, I will help you the best I can. Some questions : - what is the carrier frequency ? - do you need to implement error corrections schemes ? - do you already have an A/D converter hooked at the DSP ? if yes, brand, specs and sampling frequency ? - what is the exact reference of your DSP development kit ? EVM56002 ? - are you really obliged to mimic the various analog building blocks in digital ? - are you not interested into implementing your demodulator using a straight digital method ? In 1985, I've done a 4-DPSK modulator and demodulator using discrete analog components and CD4000 digital circuits. Including a Costas loop at the receiver, with a double balanced modulator and a quartz-pulled VCO. Carrier was at 8.192 MHz. Bit rate was 256 Kbit/s. I can assure you that if your DSP is running at 100 MHz, and if your carrier frequency is less than 20 KHz, you'll have enough Mips do the job, Use a CODEC with a sampling frequency at 44.1 or 48 KHz. With a CODEC, you have two 16-bit A/D and two 16-bit D/A. This way you'll be able to implement the modulator too, outputting the analog wave, and feeding the demodulator. Great for tests ! Great for refining your modulation schemes ! (16-QAM, ...). Therefore the EVM56002 seems the best candidate, with a Crystal Semi CODEC built-in. Or, if you find the EVM56002 a little bit obsolete, the EVM56303 seems OK. The most important point is to have the CODEC built-in on the board. I must tell you that I'm always using the Fs line of the CODEC to drive a 4.7 K resistor connected to the base of a NPN transistor hooked on the IrqA line in order to hardware-generate an interrupt on every new sample. This way, you can create a background task (reading buttons, lighting LEDs) that is transparently IrqA-interrupted by your demodulator. You never have to"wait" for a new sample. You only have to write a IrqA handler dealing with your demodulator. Far better than the littles IIR demos supplied with the EVM kit. So, if your sampling frequency is 48 KHz, you know that you nearly have 20 microsecond to do the job. Quite many instructions if you have a 50 Mips or a 100 Mips DSP ... Don't forget to save some registers at the beginning of the IrqA handler, and to restore them at the end. This because the background task is supposed to be interrupted anywhere. By the way, DONT try to program the DSP in C, especially the IrqA handler. The DSP56K series do have a nice instruction set. Easy to remember using their mnemonics. That's all for the moment. Don't hesitate in contacting me again. It is my pleasure. Stéphane CNOCKAERT BRUSSELS ----- Original Message ----- From: Jacques Malan <> To: <> Sent: Wednesday, January 05, 2000 12:12 PM Subject: [motoroladsp] where to start > Hi there, > I am a newcomer in the DSP world and would appreciate some guidance as to > where to start. > > I have designed a 4Kbit oqpsk analogue receiver and would like to implement > it in a DSP. > I have a DSP5603 development kit working at a 100Mhz. > > What I think I should do next is to take each building block of the design > i.e. a mixer a Low Pass filter,VCO etc. and some how determine how many > clockcycles each component will need and whether I will be able to fit it > into the 5603 DSP. Is there example code for these types of parts VCO etc. > I have experience in C programming but have never done a DIGITAL > demodulation design let alone on a DSP. > > I would appreciate ANY suggestions and guidance > > Thanks > Jacques > > ______________________________________________________ > > |
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