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Thread: Interest check: Camry/Scion Steering Wheel Control -> USB

  1. #41
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    What type of USB bootloader do you use?

    Before sending the PCB to production, how about upgrading your PCB-layout to include the option to mount a standard AVR 6-pin ISP box header for In-Circuit Programming for initial programming before the bootloader is loaded?
    This way you don't need to put the AVR in a programmer first, but can solder it directly on the board.
    AVRISP mkII User Guide (with ISP header pinout at page 26): http://www.atmel.com/dyn/resources/p...ISPmkII_UG.pdf

    http://www.batsocks.co.uk/readme/isp_headers.htm

  2. #42
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    Quote Originally Posted by Blues View Post
    What type of USB bootloader do you use?

    Before sending the PCB to production, how about upgrading your PCB-layout to include the option to mount a standard AVR 6-pin ISP box header for In-Circuit Programming for initial programming before the bootloader is loaded?
    This way you don't need to put the AVR in a programmer first, but can solder it directly on the board.
    AVRISP mkII User Guide (with ISP header pinout at page 26): http://www.atmel.com/dyn/resources/p...ISPmkII_UG.pdf

    http://my.opera.com/CrazyTerabyte/bl...troller-part-4
    i've considered this as well as using the TQFP version instead (to save space on the board), however I have no experience soldering these so... i'm told the oven method works? I'll see how much time I have to redesign stuff tonight.

    the bootloader is HIDBoot, I find that it works quite well.

  3. #43
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    I have no experince with the oven method. But I can easiliy handsolder a TQFP package. I also prefer to use SMD resitors over leaded types. I find it easier and faster to use SMD components, no drilling required, no bending and cutting of legs and less space required to boot. This can mean samller and hence cheaper PCBs, and less drilling can also make PCBs cheaper.
    But then again I have a lot of experince handsoldering and desoldering all types of SMD components as I have worked as a professional electronics technician, repairing electronics devices full of all sorts of tiny SMD components.
    With a bit of pratice it isn't that hard handsoldering and desoldering things like TQFP packages, but I guess it requires a bit of skills and pratice.
    Using a professional made PCB with solder mask like you have done here makes it a lot easier to solder SMD components.
    Easiest way to learn is if you know an experienced guy who can show you how to solder a TQFP package in a fast and proper way.
    Nowadays there's a lot of MSD soldering instruction videos on the internet at places like You Tube etc. Some methods better than others though and some uploaders more skilled than others. You can just serch for TQFP soldering at Google or You Tube and you will get a lot of hits.

    If you wish to make the device smaller a good idea is to use one of the red 6-pin Tyco (AMP) Micro-MaTch connectors for ISP programming instead of a standard bulky IDC Box header. Micro-MaTch are avialble both in SMD and leaded versions.
    Micro-MaTch and IDC will both fit the same standard 1.27 pitch flatcable, so you can make a ISP cable with an IDC connector at the programme end and a Micro-MaTch connector at the target end, and for this reason Micro-MaTch is also very common as ISP connectors as a more compact alternative to IDC.
    Another way to make it smaller is to use a Mini-USB or Micro-USB connector instead of a standared Type B USB connector.
    there's a big size difference as you can see:


    6-pin Micro-MaTch male and female connectors:

  4. #44
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    Quote Originally Posted by Blues View Post
    I have no experince with the oven method. But I can easiliy handsolder a TQFP package. I also prefer to use SMD resitors over leaded types. I find it easier and faster to use SMD components, no drilling required, no bending and cutting of legs and less space required to boot. This can mean samller and hence cheaper PCBs, and less drilling can also make PCBs cheaper.
    But then again I have a lot of experince handsoldering and desoldering all types of SMD components as I have worked as a professional electronics technician, repairing electronics devices full of all sorts of tiny SMD components.
    With a bit of pratice it isn't that hard handsoldering and desoldering things like TQFP packages, but I guess it requires a bit of skills and pratice.
    Using a professional made PCB with solder mask like you have done here makes it a lot easier to solder SMD components.
    Easiest way to learn is if you know an experienced guy who can show you how to solder a TQFP package in a fast and proper way.
    Nowadays there's a lot of MSD soldering instruction videos on the internet at places like You Tube etc. Some methods better than others though and some uploaders more skilled than others. You can just serch for TQFP soldering at Google or You Tube and you will get a lot of hits.

    If you wish to make the device smaller a good idea is to use one of the red 6-pin Tyco (AMP) Micro-MaTch connectors for ISP programming instead of a standard bulky IDC Box header. Micro-MaTch are avialble both in SMD and leaded versions.
    Micro-MaTch and IDC will both fit the same standard 1.27 pitch flatcable, so you can make a ISP cable with an IDC connector at the programme end and a Micro-MaTch connector at the target end, and for this reason Micro-MaTch is also very common as ISP connectors as a more compact alternative to IDC.
    Another way to make it smaller is to use a Mini-USB or Micro-USB connector instead of a standared Type B USB connector.
    there's a big size difference as you can see:


    6-pin Micro-MaTch male and female connectors:
    Ah, thanks for the wealth of information... Yes, switching to mini-B was another consideration. I think I will actually redesign the board to work with SMD then, my guess is that this will considerably lower the cost and size of the board.

    Hopefully, I don't make any mistakes though... I don't really feel like sending the circuit for prototyping again at batchpcb since they seem to take awhile...

  5. #45
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    Quote Originally Posted by no2chem View Post
    Hopefully, I don't make any mistakes though... I don't really feel like sending the circuit for prototyping again at batchpcb since they seem to take awhile...
    You can upload the schematic and pcb layout here before ordering PCBs. Then I and others can review the design and see if we have any suggestions to improvements or corrections.


    I assume you use panelization to put several identical PCBs on one large board to make PCB manufacturing cheaper?

    I haven't got any experince with BatchPCB. I live in Europe and have had good experinces with Olimex from Bulgaria for prototype PCBs, they are the cheapest I have found in Europe and still good quality solder mask, silk screen and everything. They offer de-panelization. I haven't chekced how their prices compare to BAtchPCB's, but Olimex even though Olimex doesn't offer batch production, they was still cheaper for one small PCB than the european batch manufactures I compared to.
    You can try to compare prices and delivery times, but if you live in America manybe it's cheapest and/or fastest to have them made locally.

  6. #46
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    schematic


    board


    code will come after i package it, note that the board is being revised for smd and addition of programming header

  7. #47
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    Quote Originally Posted by no2chem View Post
    the bootloader is HIDBoot, I find that it works quite well.
    Do you have a link for this?

  8. #48
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    Quote Originally Posted by Blues View Post
    Do you have a link for this?
    oh, i meant bootloadHID
    http://www.obdev.at/products/avrusb/bootloadhid.html

  9. #49
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    Before you do any layout of the new PCB you should really read and understand the relevant parts of these two AVR application notes about hardware layout and EMC considerations, especially AVR042 which points out the most important hardware design guidelines for any MCU circuits:
    AVR042: AVR Hardware Design Considerations
    AVR040: EMC Design Considerations

    The way you have routed GND and VCC traces is not a good choice. Especially the way you have placed C1 far away from the power pins it was supposed to decouple. The decoupling effect of this capacitor is decreases a lot the way you have placed it. The decoupling capacitor should be the closests thing to the MCU GND and power pins (read AVR042/AVR040).
    A car is a very noisy EMC enviroment, which just makes it even more important to follow the basic hardware and EMC layout guidelines.

    You should also add some protection to the rest pin as descirbed in section 3 of AVR042, especially now when you add an ISP connector to access from external circuit to the reset pin. It's also important to keep the crystal/resonator as close as possible to the MCU pins.

    Also a good idea to keep the USB data lines running from the USB socket to the MCU short to avoid any unnessassary EMC problems. In general it's a good idea to keep high frequnecy traces short.

    I would also add a 4.7F tantalum (or electrolytic) capacitor between GND and VCC near the USB connector as suggested in this AVR-USB example schematic: http://avrusb.wikidot.com/hardware

    A charge capacitor is especially important because the USB cable supplying the device can be quite long.
    Instead of using two zener diodes to protect the USB data lines you could alternatively add two general purpose diodes in series with VCC from the USB connector to drop the voltage supplided to the whole circuit - or use an LDO to regulate the voltage. All 3 solutions are described here, which I guess you have already read: http://avrusb.wikidot.com/hardware


    Why do you have 5 poles in your screw terminal? Isn't 3 enough?

  10. #50
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    Quote Originally Posted by Blues View Post
    Before you do any layout of the new PCB you should really read and understand the relevant parts of these two AVR application notes about hardware layout and EMC considerations, especially AVR042 which points out the most important hardware design guidelines for any MCU circuits:
    AVR042: AVR Hardware Design Considerations
    AVR040: EMC Design Considerations

    The way you have routed GND and VCC traces is not a good choice. Especially the way you have placed C1 far away from the power pins it was supposed to decouple. The decoupling effect of this capacitor is decreases a lot the way you have placed it. The decoupling capacitor should be the closests thing to the MCU GND and power pins (read AVR042/AVR040).
    A car is a very noisy EMC enviroment, which just makes it even more important to follow the basic hardware and EMC layout guidelines.

    You should also add some protection to the rest pin as descirbed in section 3 of AVR042, especially now when you add an ISP connector to access from external circuit to the reset pin. It's also important to keep the crystal/resonator as close as possible to the MCU pins.

    Also a good idea to keep the USB data lines running from the USB socket to the MCU short to avoid any unnessassary EMC problems. In general it's a good idea to keep high frequnecy traces short.

    I would also add a 4.7F tantalum (or electrolytic) capacitor between GND and VCC near the USB connector as suggested in this AVR-USB example schematic: http://avrusb.wikidot.com/hardware

    A charge capacitor is especially important because the USB cable supplying the device can be quite long.
    Instead of using two zener diodes to protect the USB data lines you could alternatively add two general purpose diodes in series with VCC from the USB connector to drop the voltage supplided to the whole circuit - or use an LDO to regulate the voltage. All 3 solutions are described here, which I guess you have already read: http://avrusb.wikidot.com/hardware


    Why do you have 5 poles in your screw terminal? Isn't 3 enough?
    ok, I'll keep these things in mind when updating the circuit. The reason I have 5 poles is because these things are supposedly designed for one wire only. I could use 4, as one is for expansion only, but early on I discovered that the steering wheel illumination ground is the same as the control ground (SWG). As a result, it is necessary to connect SWG to both the vehicle ground (for illumination) and USB ground (for ADC conversion). While my understanding of EE is slightly weak, my guess is that there is a difference in ground potential... So, as a result, pole 4 is connected to SWG, while pole 5 is connected to the vehicle ground.

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