Pecan Pico 4 – Serial Number 1 Built & Working

A new Pecan is born! I’ve received the PCBs within a week from Seeedstudio but I had to wait for a delayed delivery from digikey. I’m not really happy with the delivery times from digikey but I guess I need to blame USPS for this. I need to order from them though, because they are the only reasonable supplier for BMP180 and the GPS chip antenna. Anyways, I built up my first Pecan 4 and it worked out of the box. I was surprised that the code written for BMP085 immediately worked for BMP180 without any code changes. I still have to write some code for the RGB sensor, the EEPROM, the RTC and the beeper, but everything that worked at Pecan 3 is also working on the new PCB.

Edit: The Arduino Code and the Eagle/gerber files are on GitHub: https://github.com/tkrahn/pecanpico4

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16 thoughts on “Pecan Pico 4 – Serial Number 1 Built & Working

  1. Thomas, I received one of your previous boards a while back (from you). Can you please post a link to your work? It’s released under CC, but I can’t seem to find schematics or code to build it.
    Thanks!

  2. Thomas, I’m interested in these boards as well, I’m not sure if you’re selling them or the plans are generally available. I’ve very excited to use your work as a starting point, if I can. Thanks for any info you can share!
    Mike
    kd2eat@gmail.com

  3. Is it possible to get you avr adf7012 schematic? Im working on a similar project and would like to look at your reference

    • I think they’re not ready for selling really, and I’m not an electronics professional. Selling transmitters is also a regulation thing in most countries. I’m not able to file a FCC application or similar. However everything is open source and I’m happy to help you by answering questions if you want to build your own.

      • I’m trying right now with an arduino uno, prolific gps @ 4800baud, and an HX1-144.390-3 with no luck. I’m capable but no where near as good as you, just can’t figure it out and would rather buy one off ya. But if you say it’s contrary to law not sure what else to do other than buy a premade solution like a bigredbee or something.

      • Well, with the Arduino you’re probably on the right track. Did you try to load my Pecan code on the Uno? It might already work to a certain degree. What exactly doesn’t work for you?

      • Yup, loaded the pecanpico4 git project. Had to modify some stuff as the hx1 include doens’t have the set freq and power functions. Just did an IF. Plugged in my call, and changed the PTT pin to 4. Upped the beacon seconds to something short. Put a 493mm long wire on the HX1. As heard on radio the packets are reaaaally quiet, don’t decode, and sound kinda funny. They don’t sound like other aprs packets that are decoding just fine. I’m thinking I might have a bad HX1 or something… Doesn’t seem like your code is at fault.

      • Hmm, do you have the deviation set to the right level? How does it sound if you directly connect a headphone to the audio pin at the Uno? can you decode that if you directly plug the audio signal into your receive modem?

  4. I can decode like that yes, very interesting. I am lost when you say deviation as I’m not all that familiar with radios unfortunately. Suppose that has something to do with my situation ha. How might I check the deviation/set it properly?

  5. Hi, this is awesome. Thank you very much for sharing.
    Have you any bill of materials?
    I’ve noticed that there are some 0 value resistors.
    R4 : 0 : 0402-RES : SparkFun
    R15 : 0 : 0402-RES : SparkFun
    R21 : 0 : 0402-RES : SparkFun
    R23 : 0 : 0402-RES : SparkFun
    Can you help me?
    Thanks in advance
    David

  6. David, the 0 ohm resistors are correct – they’re just jumpers. There is a BoM for Thomas’s Pecan3, earlier in this blog which is pretty close.

    That said, if you decide to replicate this design, I’ve tried to do so and I’m not having much luck. While I’m incredibly grateful to Thomas for putting this info up, I think there’s a problem with the design with regard to the GPS chip. I’m having a great deal of trouble with GPS lock issues. Consulting with gurus on the #highaltitude IRC room, consensus is that there is probably a little too much going on around the GPS chip antenna on this board. Also, I notice (in retrospect) that there isn’t a ground plane under the GPS chip itself, which is called for in the Ublox docs. I suspect that the impedance for the GPS antenna off enough to make the reception very poor.

    I’ve learned an awful lot trying to build my Pecan4 clone, but after building 3 boards that won’t reliably lock onto GPS, I’m abandoning my efforts to use a GPS integrated with this board. For now, I’m using an Adafruit GPS breakout board lashed into the TX/RX pins that Thomas exposed on the Pecan4 board, and using the Pecan just for transmitting APRS. I’ll be designing my own board soon.

    Again, I’m immensely grateful to Thomas for sharing this design with the community, as I learned basically everything I know about trackers by building and debugging mine over the last 3 months. I intend to share my own designs and such, as I go along.

    Mike / KD2EAT@gmail.com

  7. Mike,
    Thanks for your comments. I have to confess that it sometimes takes longer to get the first lock with Pecan 3/4, but generally it works for me. All later cycle locks are as fast as 3 seconds approximately. For some reason I had bad experience with the chip antennas that I have purchased from digikey. The same model that I’ve bought from Upu works flawlessly. They look the same, but I’m not using the chip antennas from digikey anymore. You could try to replace the antenna with a simple wire that’s quarter wavelength for 1.6 GHz which worked fine for me. In general there shouldn’t be a problem with the groundplane. My error in the Pecan 3/4 design is more that the GPS receiver is too close to the Si4464 transmitter chip. Note that we use 100 mW rather than 10 mW in the UK, so while transmitting the AGC of the GPS receiver will almost shut down because of the high noise level. That makes it difficult to transmit and receive at the same time. The Pecan 5/6 design separates the TX chip further from the GPS so I hope this will improve.

    • Thomas, interesting thought on the antennas. I’m running with digi-key ones. If I put a GPS on another board, I may try your suggestion.

      I’m using Max7c’s. Though the specs indicate they should be 1 DBM better on receive, some comments on #highaltitude indicate that other people are finding them LESS sensitive as well. Are you running 6s or 7s?

      Regarding transmit, yes, I noticed that problem. I was running diagnostics, capturing the GPS output over I2C, and I could watch the GPS starting to acquire satellites in the GPGSV messages. Then, it would do a transmit, and the GPGSV satellite count got knocked back to 0 or 1, and it started over. I eventually modified the code so that it wouldn’t send any APRS strings until after the first GPS lock. That helped. The biggest help was removing the SMA connector and soldering on antenna wires. Still, it’s jut not reliable enough for me to fly. Perhaps I’m suffering the chip antenna problem as well.

      Mike

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