We are using the Microchip MRF24JA40 802.15.4 RF transceiver, might look into Atmel's AT86RF231 and Freescale's MC13202 as well. We have one working board talking to a Microchip pre-made module, but two non-working boards. The only difference is the crystal. The working one is 5 mm SMD and the non-working one is 11 mm 2 pins. Could it be so sensitive to crystal selection? Do we need to pre-screen them for productions? The Freescale chip allows crystal calibration, but won't solve drift problem. My non-working board detects signals occasionally, but not good enough to pull in any packet. It seems to be drifting in and out of the channel. Also, the 1/4 length for 2.5GHz is 3cm. Most WiFI antenna seems to be bigger. Are they 3/4 length? Would 1-1/4 be better? We are just using a wire coiled on top of the PCB.
802.15.4 RF issues
Started by ●October 27, 2012
Reply by ●October 27, 20122012-10-27
On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote:> We are using the Microchip MRF24JA40 802.15.4 RF transceiver, > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. �We > have one working board talking to a Microchip pre-made module, but two > non-working boards. �The only difference is the crystal. �The working > one is 5 mm SMD and the non-working one is 11 mm 2 pins. �Could it be > so sensitive to crystal selection? �Do we need to pre-screen them for > productions? >a different crystal will probably need different capacitors to be spot on frequency. Try measuring the frequency, 802.15.4 requires something like +/-40ppm> The Freescale chip allows crystal calibration, but won't solve drift > problem. �My non-working board detects signals occasionally, but not > good enough to pull in any packet. �It seems to be drifting in and out > of the channel.I believe if you get the caps right wor the crystal you should able to stay with in +/40ppm over temperature and aging> > Also, the 1/4 length for 2.5GHz is 3cm. �Most WiFI antenna seems to be > bigger. �Are they 3/4 length? �Would 1-1/4 be better? �We are just > using a wire coiled on top of the PCB.all kinds of different antennas as long as it is matched I'd assume what ever their put on give an acceptable performance but if devices are close I don't think it matters much I worked on developing the freescale 802.15.4 stuff but that was many years ago -Lasse
Reply by ●October 27, 20122012-10-27
On Oct 27, 10:41�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote:> On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote: > > > We are using the Microchip MRF24JA40 802.15.4 RF transceiver, > > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. �We > > have one working board talking to a Microchip pre-made module, but two > > non-working boards. �The only difference is the crystal. �The working > > one is 5 mm SMD and the non-working one is 11 mm 2 pins. �Could it be > > so sensitive to crystal selection? �Do we need to pre-screen them for > > productions? > > a different crystal will probably need different capacitors to be > spot > on frequency. Try measuring the frequency, 802.15.4 requires > something > like +/-40ppmThe non-working one says 20ppm, not sure if it's stability or tolerence. However, the cheap stuff (10 for $1.95 including shipping from Hong Kong) might be fake. The working one (80 cents + $3 shipping from digikey) is actually 30ppm. Will try to order more test crystals later.> > > The Freescale chip allows crystal calibration, but won't solve drift > > problem. �My non-working board detects signals occasionally, but not > > good enough to pull in any packet. �It seems to be drifting in and out > > of the channel. > > I believe if you get the caps right wor the crystal you should able > to > stay with in +/40ppm over temperature and aging > > > > > Also, the 1/4 length for 2.5GHz is 3cm. �Most WiFI antenna seems to be > > bigger. �Are they 3/4 length? �Would 1-1/4 be better? �We are just > > using a wire coiled on top of the PCB. > > all kinds of different antennas as long as it is matched I'd assume > what > ever their put on give an acceptable performance > > but if devices are close I don't think it matters much > > I worked on developing the freescale 802.15.4 stuff but that was many > years ago > > -LasseI have a 9cm wire talking to the Microchip's PCB E antenna. My signal (on the devices) is much weaker than the Microchip module (coordinator), but seems to be OK.
Reply by ●October 27, 20122012-10-27
On 27 Okt., 19:59, linnix <m...@linnix.info-for.us> wrote:> On Oct 27, 10:41�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote: > > > > We are using the Microchip MRF24JA40 802.15.4 RF transceiver, > > > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. �We > > > have one working board talking to a Microchip pre-made module, but two > > > non-working boards. �The only difference is the crystal. �The working > > > one is 5 mm SMD and the non-working one is 11 mm 2 pins. �Could it be > > > so sensitive to crystal selection? �Do we need to pre-screen them for > > > productions? > > > a different crystal will probably need different capacitors to be > > spot > > on frequency. Try measuring the frequency, 802.15.4 requires > > something > > like +/-40ppm > > The non-working one says 20ppm, not sure if it's stability or > tolerence. �However, the cheap stuff (10 for $1.95 including shipping > from Hong Kong) might be fake. �The working one (80 cents + $3 > shipping from digikey) is actually 30ppm. �Will try to order more test > crystals later. >my point is that for each different type of xtal you need to measure the resulting frequency and adjust the caps, it can be much more than 40ppm off> > > > The Freescale chip allows crystal calibration, but won't solve drift > > > problem. �My non-working board detects signals occasionally, but not > > > good enough to pull in any packet. �It seems to be drifting in and out > > > of the channel. > > > I believe if you get the caps right wor the crystal you should able > > to > > stay with in +/40ppm over temperature and aging > > > > Also, the 1/4 length for 2.5GHz is 3cm. �Most WiFI antenna seems to be > > > bigger. �Are they 3/4 length? �Would 1-1/4 be better? �We are just > > > using a wire coiled on top of the PCB. > > > all kinds of different antennas as long as it is matched I'd assume > > what > > ever their put on give an acceptable performance > > > but if devices are close I don't think it matters much > > > I worked on developing the freescale 802.15.4 stuff but that was many > > years ago > > > -Lasse > > I have a 9cm wire talking to the Microchip's PCB E antenna. �My signal > (on the devices) is much weaker than the Microchip module > (coordinator), but seems to be OK.-Lasse
Reply by ●October 27, 20122012-10-27
On Sat, 27 Oct 2012 10:59:34 -0700, linnix wrote:> On Oct 27, 10:41 am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: >> On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote: >> >> > We are using the Microchip MRF24JA40 802.15.4 RF transceiver, >> > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. >> > We have one working board talking to a Microchip pre-made module, >> > but two non-working boards. The only difference is the crystal. The >> > working one is 5 mm SMD and the non-working one is 11 mm 2 pins. >> > Could it be so sensitive to crystal selection? Do we need to >> > pre-screen them for productions? >> >> a different crystal will probably need different capacitors to be spot >> on frequency. Try measuring the frequency, 802.15.4 requires something >> like +/-40ppm > > The non-working one says 20ppm, not sure if it's stability or tolerence. > However, the cheap stuff (10 for $1.95 including shipping from Hong > Kong) might be fake. The working one (80 cents + $3 shipping from > digikey) is actually 30ppm. Will try to order more test crystals later. > > >> > The Freescale chip allows crystal calibration, but won't solve drift >> > problem. My non-working board detects signals occasionally, but not >> > good enough to pull in any packet. It seems to be drifting in and >> > out of the channel. >> >> I believe if you get the caps right wor the crystal you should able to >> stay with in +/40ppm over temperature and aging >> >> >> >> > Also, the 1/4 length for 2.5GHz is 3cm. Most WiFI antenna seems to >> > be bigger. Are they 3/4 length? Would 1-1/4 be better? We are just >> > using a wire coiled on top of the PCB. >> >> all kinds of different antennas as long as it is matched I'd assume >> what ever their put on give an acceptable performance >> >> but if devices are close I don't think it matters much >> >> I worked on developing the freescale 802.15.4 stuff but that was many >> years ago >> >> -Lasse > > I have a 9cm wire talking to the Microchip's PCB E antenna. My signal > (on the devices) is much weaker than the Microchip module (coordinator), > but seems to be OK.Pay attention to parasitic capacitances on the PCB, too. If you've got ground plane underneath your crystal lands, then you've got capacitors, and those capacitors' temperature behavior is no better than the PCB material's. See if your manufacturer of choice has any app notes on layout for good oscillator stability. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
Reply by ●October 27, 20122012-10-27
On Oct 27, 11:21�am, Tim Wescott <t...@seemywebsite.please> wrote:> On Sat, 27 Oct 2012 10:59:34 -0700, linnix wrote: > > On Oct 27, 10:41�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > >> On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote: > > >> > We are using the Microchip MRF24JA40 802.15.4 RF transceiver, > >> > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. > >> > �We have one working board talking to a Microchip pre-made module, > >> > but two non-working boards. �The only difference is the crystal. �The > >> > working one is 5 mm SMD and the non-working one is 11 mm 2 pins. > >> > �Could it be so sensitive to crystal selection? �Do we need to > >> > pre-screen them for productions? > > >> a different crystal will probably need different capacitors to be spot > >> on frequency. Try measuring the frequency, 802.15.4 requires something > >> like +/-40ppm > > > The non-working one says 20ppm, not sure if it's stability or tolerence. > > �However, the cheap stuff (10 for $1.95 including shipping from Hong > > Kong) might be fake. �The working one (80 cents + $3 shipping from > > digikey) is actually 30ppm. �Will try to order more test crystals later. > > >> > The Freescale chip allows crystal calibration, but won't solve drift > >> > problem. �My non-working board detects signals occasionally, but not > >> > good enough to pull in any packet. �It seems to be drifting in and > >> > out of the channel. > > >> I believe if you get the caps right wor the crystal you should able to > >> stay with in +/40ppm over temperature and aging > > >> > Also, the 1/4 length for 2.5GHz is 3cm. �Most WiFI antenna seems to > >> > be bigger. �Are they 3/4 length? �Would 1-1/4 be better? �We are just > >> > using a wire coiled on top of the PCB. > > >> all kinds of different antennas as long as it is matched I'd assume > >> what ever their put on give an acceptable performance > > >> but if devices are close I don't think it matters much > > >> I worked on developing the freescale 802.15.4 stuff but that was many > >> years ago > > >> -Lasse > > > I have a 9cm wire talking to the Microchip's PCB E antenna. �My signal > > (on the devices) is much weaker than the Microchip module (coordinator), > > but seems to be OK. > > Pay attention to parasitic capacitances on the PCB, too. �If you've got > ground plane underneath your crystal lands, then you've got capacitors, > and those capacitors' temperature behavior is no better than the PCB > material's.Yes, will have better layout for next version.> > See if your manufacturer of choice has any app notes on layout for good > oscillator stability.They suggested 4 layers with 4 ground plane (Digital, Analog, Crystal and RF). But that would be too expensive. I am cutting corners with 2 layers. Perhaps i am just lucky with the one working board.
Reply by ●October 27, 20122012-10-27
On Oct 27, 11:18�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote:> On 27 Okt., 19:59, linnix <m...@linnix.info-for.us> wrote: > > > > > > > On Oct 27, 10:41�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > > On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote: > > > > > We are using the Microchip MRF24JA40 802.15.4 RF transceiver, > > > > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. �We > > > > have one working board talking to a Microchip pre-made module, but two > > > > non-working boards. �The only difference is the crystal. �The working > > > > one is 5 mm SMD and the non-working one is 11 mm 2 pins. �Could it be > > > > so sensitive to crystal selection? �Do we need to pre-screen them for > > > > productions? > > > > a different crystal will probably need different capacitors to be > > > spot > > > on frequency. Try measuring the frequency, 802.15.4 requires > > > something > > > like +/-40ppm > > > The non-working one says 20ppm, not sure if it's stability or > > tolerence. �However, the cheap stuff (10 for $1.95 including shipping > > from Hong Kong) might be fake. �The working one (80 cents + $3 > > shipping from digikey) is actually 30ppm. �Will try to order more test > > crystals later. > > my point is that for each different type of xtal you need to measure > the resulting frequency and adjust the caps, it can be much more than > 40ppm > offUntil i get the 2.5GHz frequency counter, i just have to keep trying different crystals and caps. I wonder if it's because of the ceramic SMD vs. metal case HC-59 crystal, in terms of para. caps.
Reply by ●October 27, 20122012-10-27
On 27 Okt., 20:42, linnix <m...@linnix.info-for.us> wrote:> On Oct 27, 11:18�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > > > > > > > > > On 27 Okt., 19:59, linnix <m...@linnix.info-for.us> wrote: > > > > On Oct 27, 10:41�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > > > On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote: > > > > > > We are using the Microchip MRF24JA40 802.15.4 RF transceiver, > > > > > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. �We > > > > > have one working board talking to a Microchip pre-made module, but two > > > > > non-working boards. �The only difference is the crystal. �The working > > > > > one is 5 mm SMD and the non-working one is 11 mm 2 pins. �Could it be > > > > > so sensitive to crystal selection? �Do we need to pre-screen them for > > > > > productions? > > > > > a different crystal will probably need different capacitors to be > > > > spot > > > > on frequency. Try measuring the frequency, 802.15.4 requires > > > > something > > > > like +/-40ppm > > > > The non-working one says 20ppm, not sure if it's stability or > > > tolerence. �However, the cheap stuff (10 for $1.95 including shipping > > > from Hong Kong) might be fake. �The working one (80 cents + $3 > > > shipping from digikey) is actually 30ppm. �Will try to order more test > > > crystals later. > > > my point is that for each different type of xtal you need to measure > > the resulting frequency and adjust the caps, it can be much more than > > 40ppm > > off > > Until i get the 2.5GHz frequency counter, i just have to keep trying > different crystals and caps. �I wonder if it's because of the ceramic > SMD vs. metal case HC-59 crystal, in terms of para. caps.you can just measure the xtal frequency -Lasse
Reply by ●October 27, 20122012-10-27
On Oct 27, 11:48�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote:> On 27 Okt., 20:42, linnix <m...@linnix.info-for.us> wrote: > > > > > > > On Oct 27, 11:18�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > > On 27 Okt., 19:59, linnix <m...@linnix.info-for.us> wrote: > > > > > On Oct 27, 10:41�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > > > > On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote: > > > > > > > We are using the Microchip MRF24JA40 802.15.4 RF transceiver, > > > > > > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. �We > > > > > > have one working board talking to a Microchip pre-made module, but two > > > > > > non-working boards. �The only difference is the crystal. �The working > > > > > > one is 5 mm SMD and the non-working one is 11 mm 2 pins. �Could it be > > > > > > so sensitive to crystal selection? �Do we need to pre-screen them for > > > > > > productions? > > > > > > a different crystal will probably need different capacitors to be > > > > > spot > > > > > on frequency. Try measuring the frequency, 802.15.4 requires > > > > > something > > > > > like +/-40ppm > > > > > The non-working one says 20ppm, not sure if it's stability or > > > > tolerence. �However, the cheap stuff (10 for $1.95 including shipping > > > > from Hong Kong) might be fake. �The working one (80 cents + $3 > > > > shipping from digikey) is actually 30ppm. �Will try to order more test > > > > crystals later. > > > > my point is that for each different type of xtal you need to measure > > > the resulting frequency and adjust the caps, it can be much more than > > > 40ppm > > > off > > > Until i get the 2.5GHz frequency counter, i just have to keep trying > > different crystals and caps. �I wonder if it's because of the ceramic > > SMD vs. metal case HC-59 crystal, in terms of para. caps. > > you can just measure the xtal frequency > > -LasseWould it be possible to temperature compensate the crystal with the MC13202? That might force us to switch part.
Reply by ●October 27, 20122012-10-27
On 27 Okt., 20:52, linnix <m...@linnix.info-for.us> wrote:> On Oct 27, 11:48�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > > > > > > > > > On 27 Okt., 20:42, linnix <m...@linnix.info-for.us> wrote: > > > > On Oct 27, 11:18�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > > > On 27 Okt., 19:59, linnix <m...@linnix.info-for.us> wrote: > > > > > > On Oct 27, 10:41�am, "langw...@fonz.dk" <langw...@fonz.dk> wrote: > > > > > > > On 27 Okt., 19:22, linnix <m...@linnix.info-for.us> wrote: > > > > > > > > We are using the Microchip MRF24JA40 802.15.4 RF transceiver, > > > > > > > might look into Atmel's AT86RF231 and Freescale's MC13202 as well. �We > > > > > > > have one working board talking to a Microchip pre-made module, but two > > > > > > > non-working boards. �The only difference is the crystal. �The working > > > > > > > one is 5 mm SMD and the non-working one is 11 mm 2 pins. �Could it be > > > > > > > so sensitive to crystal selection? �Do we need to pre-screen them for > > > > > > > productions? > > > > > > > a different crystal will probably need different capacitors to be > > > > > > spot > > > > > > on frequency. Try measuring the frequency, 802.15.4 requires > > > > > > something > > > > > > like +/-40ppm > > > > > > The non-working one says 20ppm, not sure if it's stability or > > > > > tolerence. �However, the cheap stuff (10 for $1.95 including shipping > > > > > from Hong Kong) might be fake. �The working one (80 cents + $3 > > > > > shipping from digikey) is actually 30ppm. �Will try to order more test > > > > > crystals later. > > > > > my point is that for each different type of xtal you need to measure > > > > the resulting frequency and adjust the caps, it can be much more than > > > > 40ppm > > > > off > > > > Until i get the 2.5GHz frequency counter, i just have to keep trying > > > different crystals and caps. �I wonder if it's because of the ceramic > > > SMD vs. metal case HC-59 crystal, in terms of para. caps. > > > you can just measure the xtal frequency > > > -Lasse > > Would it be possible to temperature compensate the crystal with the > MC13202? �That might force us to switch part.http://cache.freescale.com/files/rf_if/doc/app_note/AN3251.pdf seems to indicated that is wouldn't be necessary but with the switchable load caps and temperature measurement I guess you could -Lasse
