Comments for White Rose Engineering http://lackawanna.hackhut.com Just another HackHut site Wed, 01 Aug 2012 05:19:35 +0000 hourly 1 http://wordpress.org/?v=3.0.5 Comment on Easy I2C: Pull-ups optional by lackawanna http://lackawanna.hackhut.com/2011/10/10/easy-i2c/#comment-2096 lackawanna Wed, 01 Aug 2012 05:19:35 +0000 http://lackawanna.hackhut.com/?p=375#comment-2096 It sounds like you are setting the external resistors right. 10k is sufficient at 100kHz, so 4.7k per line is more than enough. It does not matter I believe where the pullup resistor is placed on the line - say either close to the AVR master or at the end next to the slave - since the line will be short enough to be considered lumped. That is it will not behave as a transmission line where reflections will result should the line not be properly terminated at the master and the slave. Maybe you are having problems because of the stk600. Also don't enable the pull-up as I did in the code above. That is make sure these two lines are omitted from your code: SCL_PORT |= _BV(SCL_BIT); // enable pull up on TWI clock line SDA_PORT |= _BV(SDA_BIT); // enable pull up on TWI data line I should of pointed this out in my post. It sounds like you are setting the external resistors right. 10k is sufficient at 100kHz, so 4.7k per line is more than enough. It does not matter I believe where the pullup resistor is placed on the line – say either close to the AVR master or at the end next to the slave – since the line will be short enough to be considered lumped. That is it will not behave as a transmission line where reflections will result should the line not be properly terminated at the master and the slave. Maybe you are having problems because of the stk600. Also don’t enable the pull-up as I did in the code above. That is make sure these two lines are omitted from your code:

SCL_PORT |= _BV(SCL_BIT); // enable pull up on TWI clock line
SDA_PORT |= _BV(SDA_BIT); // enable pull up on TWI data line

I should of pointed this out in my post.

]]> Comment on Easy I2C: Pull-ups optional by nippi1111 http://lackawanna.hackhut.com/2011/10/10/easy-i2c/#comment-2091 nippi1111 Tue, 31 Jul 2012 14:12:50 +0000 http://lackawanna.hackhut.com/?p=375#comment-2091 hey, i am using at2560. .i dont want use internal pullups.i am using bus at 100khz bus speed i hav used 2 4k7 pullups but i am not getting in which side should i give vcc to pull from slave or master.pls help will b highle apperiaciated and not to mention i am using stk600 and they use 2 different spi and voltage supplies and dont have common grnd or common vcc.any help,,,pls pls hey,
i am using at2560. .i dont want use internal pullups.i am using bus at 100khz bus speed i hav used 2 4k7 pullups but i am not getting in which side should i give vcc to pull from slave or master.pls help will b highle apperiaciated and not to mention i am using stk600 and they use 2 different spi and voltage supplies and dont have common grnd or common vcc.any help,,,pls pls

]]> Comment on Using V-USB and the HID Class (Part I of III) by Coda http://lackawanna.hackhut.com/2011/10/04/using-v-usb-and-the-hid-class-part-i/#comment-1735 Coda Sun, 10 Jun 2012 16:35:14 +0000 http://lackawanna.hackhut.com/?p=87#comment-1735 Great article, and I concur; I've made several V-USB projects with 12Mhz Resonators rather than crystals, and they seem to work fine. I have obtained a few 16 and 20Mhz resonators for future projects (if they work fine with V-USB why bother using crystals for non-V-USB projects that don't require strict timing...?) Great article, and I concur; I’ve made several V-USB projects with 12Mhz Resonators rather than crystals, and they seem to work fine. I have obtained a few 16 and 20Mhz resonators for future projects (if they work fine with V-USB why bother using crystals for non-V-USB projects that don’t require strict timing…?)

]]> Comment on Using V-USB and the HID Class (Part I of III) by lackawanna http://lackawanna.hackhut.com/2011/10/04/using-v-usb-and-the-hid-class-part-i/#comment-1712 lackawanna Tue, 05 Jun 2012 04:44:29 +0000 http://lackawanna.hackhut.com/?p=87#comment-1712 It is noteworthy! Thank you for the kind words as well. I rather reserve the crystal for other precision uses rather than for the sake of the usb interface. It is noteworthy! Thank you for the kind words as well. I rather reserve the crystal for other precision uses rather than for the sake of the usb interface.

]]> Comment on Using V-USB and the HID Class (Part III of III) by lackawanna http://lackawanna.hackhut.com/2011/10/06/using-v-usb-and-the-hid-class-part-iiiiii/#comment-1711 lackawanna Tue, 05 Jun 2012 04:36:34 +0000 http://lackawanna.hackhut.com/?p=324#comment-1711 Try running it using sudo. See if that works. Namely, try: $ sudo ./simple If that does work then you likely need to add a file to /dev/udev to make /dev/hidraw0 read-writable from user space. See part two. Otherwise if it doesn't work, make sure the usb device you connected to your computer is being recognized. It should also create a /dev/hidraw0 device file when it registers itself as a hid device. FYI, I found out that there is a function call in libusb which will force the kernel to release /dev/hidraw0 so libusb can use it. I didn't mention that fact in my writeup unfortunately. I only learned about it later. It's a important point, nevertheless I believe you still have to be superuser to force the kernel to release it through libusb which is a big negative in my view. Try running it using sudo. See if that works. Namely, try:

$ sudo ./simple

If that does work then you likely need to add a file to /dev/udev to make /dev/hidraw0 read-writable from user space. See part two. Otherwise if it doesn’t work, make sure the usb device you connected to your computer is being recognized. It should also create a /dev/hidraw0 device file when it registers itself as a hid device. FYI, I found out that there is a function call in libusb which will force the kernel to release /dev/hidraw0 so libusb can use it. I didn’t mention that fact in my writeup unfortunately. I only learned about it later. It’s a important point, nevertheless I believe you still have to be superuser to force the kernel to release it through libusb which is a big negative in my view.

]]> Comment on Using V-USB and the HID Class (Part III of III) by ChinnyxD http://lackawanna.hackhut.com/2011/10/06/using-v-usb-and-the-hid-class-part-iiiiii/#comment-1702 ChinnyxD Sun, 03 Jun 2012 14:41:37 +0000 http://lackawanna.hackhut.com/?p=324#comment-1702 Very nice tutorial! But I have some trouble running the simple.c program. When i run the program it says: write: bad file descriptor.. Could anyone explain how to fix this?? Much appreciated! Very nice tutorial! But I have some trouble running the simple.c program. When i run the program it says: write: bad file descriptor.. Could anyone explain how to fix this??

Much appreciated!

]]> Comment on Using V-USB and the HID Class (Part I of III) by con-f-use http://lackawanna.hackhut.com/2011/10/04/using-v-usb-and-the-hid-class-part-i/#comment-1678 con-f-use Thu, 31 May 2012 16:05:22 +0000 http://lackawanna.hackhut.com/?p=87#comment-1678 Thanks for this. It's well written article series! However I've found ceramic oscillators as well as the on board RC oscillator of (e.g.) the AtMega168 sufficient to run v-usb in 12MHz mode. I have tested it myself with the version of Jan 2012. Thought that might be noteworthy. Thanks for this. It’s well written article series!

However I’ve found ceramic oscillators as well as the on board RC oscillator of (e.g.) the AtMega168 sufficient to run v-usb in 12MHz mode. I have tested it myself with the version of Jan 2012. Thought that might be noteworthy.

]]> Comment on Easy I2C: Pull-ups optional by lackawanna http://lackawanna.hackhut.com/2011/10/10/easy-i2c/#comment-1628 lackawanna Sun, 20 May 2012 02:25:44 +0000 http://lackawanna.hackhut.com/?p=375#comment-1628 Here is the quote from Myke Predko: “I2C connections between the PIC microcontroller’s I2C SDA (data) and SCL (clock) pins is very simple, with just a pull-up on each line, as shown in Fig. 16.15. I typically use a 1-kohm resistor for 400-kHz data transfers and a 10kohm resistor for 100-kHz data rates.” Here is the quote from Myke Predko: “I2C connections between the PIC microcontroller’s I2C SDA (data) and SCL (clock) pins is very simple, with just a pull-up on each line, as shown in Fig. 16.15. I typically use a 1-kohm resistor for 400-kHz data transfers and a 10kohm resistor for 100-kHz data rates.”

]]> Comment on Easy I2C: Pull-ups optional by lackawanna http://lackawanna.hackhut.com/2011/10/10/easy-i2c/#comment-1622 lackawanna Sat, 19 May 2012 04:39:55 +0000 http://lackawanna.hackhut.com/?p=375#comment-1622 Thank you for the kind suggestion! It is very appreciated. You might want to consider one of the USB based xbees. Or you can use the uart-based xbees and interface from your computer through a FTDI cable. One of my best decisions ever was to buy a FTDI cable - it allowed me concentrate on AVR design instead of worrying about building a max232 circuit. Your question seems to indicate you want to run a xbee off your computer. If however you want to run a xbee from your AVR you only need to use the UART, no level conversion is needed. Anyway, you have spurned me to write a wireless article. Until then see this site for a cool wireless/remote control design http://dl.dropbox.com/u/43021514/CWTD/RemoteControl/May15.html Thank you for the kind suggestion! It is very appreciated. You might want to consider one of the USB based xbees. Or you can use the uart-based xbees and interface from your computer through a FTDI cable. One of my best decisions ever was to buy a FTDI cable – it allowed me concentrate on AVR design instead of worrying about building a max232 circuit. Your question seems to indicate you want to run a xbee off your computer.

If however you want to run a xbee from your AVR you only need to use the UART, no level conversion is needed. Anyway, you have spurned me to write a wireless article. Until then see this site for a cool wireless/remote control design http://dl.dropbox.com/u/43021514/CWTD/RemoteControl/May15.html

]]> Comment on Easy I2C: Pull-ups optional by Bishal Paudel http://lackawanna.hackhut.com/2011/10/10/easy-i2c/#comment-1615 Bishal Paudel Fri, 18 May 2012 02:01:19 +0000 http://lackawanna.hackhut.com/?p=375#comment-1615 Can you make a detailed post like this on XBee (using max232 for connection with X-CTU)? Can you make a detailed post like this on XBee (using max232 for connection with X-CTU)?

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