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by Richard-TX
Tue Dec 31, 2013 9:59 pm
Forum: Beginners
Topic: MPU-6050 is not being displayed in i2c address table
Replies: 6
Views: 5894

Re: MPU-6050 is not being displayed in i2c address table

you have not indicated if you have the address line tied high or low. The address line should not be left floating unless the manufacturer says it is ok to do so.
by Richard-TX
Tue Dec 31, 2013 3:34 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Does i2c need pullups (resistors, not diapers!)
Replies: 25
Views: 13528

Re: Does i2c need pullups (resistors, not diapers!)

Agreed and good advice. Know what you are doing when playing with +5 volts.
by Richard-TX
Tue Dec 31, 2013 4:50 am
Forum: General discussion
Topic: Blinking Text.
Replies: 6
Views: 1443

Re: Blinking Text.

add a 0.5 second sleep?
by Richard-TX
Tue Dec 31, 2013 4:43 am
Forum: Beginners
Topic: file transfer
Replies: 4
Views: 616

Re: file transfer

The only way without a network connection is to remove the SD card from the Rpi and plug it into a sd adapter on your pc.
by Richard-TX
Tue Dec 31, 2013 4:39 am
Forum: General discussion
Topic: 4x3 keypad?
Replies: 2
Views: 547

Re: 4x3 keypad?

Yes. It is called muti-threaded interrupts.

http://raspi.tv/2013/how-to-use-interru ... pio-part-3
by Richard-TX
Tue Dec 31, 2013 12:23 am
Forum: Troubleshooting
Topic: Volume was not properly unmounted ...
Replies: 46
Views: 129934

Volume was not properly unmounted ...

Here is the fix for this annoying message. # dmesg | grep corrupt [ 21.280705] FAT-fs (mmcblk0p1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck. # umount /boot # git clone http://daniel-baumann.ch/git/software/dosfstools.git # cd dosfstools # make cc -O2 -fomit-frame-...
by Richard-TX
Mon Dec 30, 2013 9:51 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Does i2c need pullups (resistors, not diapers!)
Replies: 25
Views: 13528

Re: Does i2c need pullups (resistors, not diapers!)

When dealing with I2c devices it is indeed important to make sure that the specs of the device are adhered to. Some devices want a VDD of 5 volts, others like the PCA9685 will take anything from 2.3 to 5.5 volts, etc. In the case of the PCA9544 mux, different buses with different voltages can be mix...
by Richard-TX
Mon Dec 30, 2013 8:14 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Using Slice of Pi/o and 16x2 LCD at the same time?
Replies: 30
Views: 7946

Re: Using Slice of Pi/o and 16x2 LCD at the same time?

You are correct but it depends on what is on the bus. In the case of the PCA9685, address 0x70 is used as well as it's normal 0x40 address. This is due to the all-call feature.


Image
by Richard-TX
Mon Dec 30, 2013 7:34 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Using Slice of Pi/o and 16x2 LCD at the same time?
Replies: 30
Views: 7946

Re: Using Slice of Pi/o and 16x2 LCD at the same time?

If you really want to go nuts, get a I2C Mux. Add up to sixty I2C buses to the Rpi. (address 0x70 is already used on on I2c bus on the Rpi) http://dsscircuits.com/i2c-multiplexer.html http://dsscircuits.com/images/images/I2C%20Multiplexer%20RevB.jpg http://www.nxp.com/documents/data_sheet/PCF8574_PC...
by Richard-TX
Mon Dec 30, 2013 7:28 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Using Slice of Pi/o and 16x2 LCD at the same time?
Replies: 30
Views: 7946

Re: Using Slice of Pi/o and 16x2 LCD at the same time?

Adafruit has drivers and tutorial for driving a display with a MCP23008. There is no reason why a MCP23017 could not be used. See http://learn.adafruit.com/i2c-spi-lcd-backpack With a max of 8 23017 chips per bus and two LCD displays per chip, you could drive 16 displays on one bus. Use both I2c Bus...
by Richard-TX
Mon Dec 30, 2013 7:10 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Does i2c need pullups (resistors, not diapers!)
Replies: 25
Views: 13528

Re: Does i2c need pullups (resistors, not diapers!)

My estimate is that 10K is too high for a 400KHz I2C bus. I use ~2K for 3V3 and ~3K for 5V. I have used 10k with the Rpi I2c bus at 1 Mhz speeds (Fast Mode +) with no issues. Cables have to be Cat5/6, the SDA and SCL signals have to be a twisted pair with ground but other than that no special consi...
by Richard-TX
Mon Dec 30, 2013 3:41 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: PCF8574AP I2C LED's
Replies: 10
Views: 4576

Re: PCF8574AP I2C LED's

I happen to like the MCP23017. There are many tutorials around that chip. Cost is under $2 each. Lots of I-O with that chip as it has 16 ports. Back to the 8574. I know reading a data sheet is difficult. The point was to get you to ask about the control register. Since the device defaults to inputs,...
by Richard-TX
Mon Dec 30, 2013 12:47 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: PCF8574AP I2C LED's
Replies: 10
Views: 4576

Re: PCF8574AP I2C LED's

pi@raspberrypi ~/scripts $ sudo i2cset -y 1 0x38 0xff 0xff
referring to the data sheet at http://www.nxp.com/documents/data_sheet ... F8574A.pdf try to find out why you would want or not want to write at location 0xff a value of 0xff.
by Richard-TX
Mon Dec 30, 2013 10:42 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: PCF8574AP I2C LED's
Replies: 10
Views: 4576

Re: PCF8574AP I2C LED's

do the following

Code: Select all

i2cdump 1 0x38
and post the results
by Richard-TX
Mon Dec 30, 2013 1:15 am
Forum: Networking and servers
Topic: Can I run DNS, DLNA, network shares, and Shairport?
Replies: 2
Views: 1264

Re: Can I run DNS, DLNA, network shares, and Shairport?

It isn't the service that you add that is going to determine the load on the Rpi, it is how CPU or I-O intensive the application is. DNS and DHCP is neither CPU or I-O intensive so unless you have an errant client asking for name resolution or a new IP a few thousand times a second, there will no im...
by Richard-TX
Mon Dec 30, 2013 1:03 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Does i2c need pullups (resistors, not diapers!)
Replies: 25
Views: 13528

Re: Does i2c need pullups (resistors, not diapers!)

Take a look at what Adafruit does with their 16 port i2c based led/servo controller. Another way to look at it is that if Adafruit uses 10k ohm resistors and 32 of their devices can be placed on a I2C bus, then 10k must be about right. http://rocpi.ae-tool.com/docs/Adafruit%20PCA9685.PNG right click...
by Richard-TX
Sun Dec 29, 2013 10:54 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Does i2c need pullups (resistors, not diapers!)
Replies: 25
Views: 13528

Re: Does i2c need pullups (resistors, not diapers!)

Just put 10 k resistors between SDA and SCL and VDD with every chip you add to the bus.
by Richard-TX
Sun Dec 29, 2013 10:52 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: PCF8574AP I2C LED's
Replies: 10
Views: 4576

Re: PCF8574AP I2C LED's

Dougie is right. you need 0x38 to be declared, not 38.

I find it is helpful to first do what you need with i2cset and i2cget. Then once it is fully understood, then translate that to python, c, etc.
by Richard-TX
Sun Dec 29, 2013 10:43 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: RTC Clock - Why?
Replies: 6
Views: 1655

Re: RTC Clock - Why?

DougieLawson wrote:Oh yes, I have an Ubuntu server that runs ntpd.
Currently synced to five stratum 2 servers.
I even ran it with my Garmin ETrex hooked up to get a stratum 0 time ref for an experiment.
That is pretty hard core. That is a lot more precision than I would ever need.
by Richard-TX
Sun Dec 29, 2013 6:52 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: RTC Clock - Why?
Replies: 6
Views: 1655

Re: RTC Clock - Why?

What if you want good timing but don't have a good connection to the Internets? A DS1307 breakout board (like the one my twin brother got me for Xmas) costs less than a tenner. I guess I am absolutely dependent on a fast connection to the internet. Even without that, I would have one machine in the...
by Richard-TX
Sun Dec 29, 2013 6:29 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: RTC Clock - Why?
Replies: 6
Views: 1655

RTC Clock - Why?

Why add a RTC clock? The long term accuracy of ntp is far better than any RTC.
by Richard-TX
Sun Dec 29, 2013 6:11 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Interfacing Raspberry Pi with RTC1307 without level shifter?
Replies: 31
Views: 7124

Re: Interfacing Raspberry Pi with RTC1307 without level shif

The author says this.

"The device is running at 5V, but logic levels are running at just 2V2 - so you don’t need to worry since RPi can just handle a maximum of 3V3 at logic levels..."

As a result level shifters are not needed.
by Richard-TX
Sun Dec 29, 2013 6:02 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Does i2c need pullups (resistors, not diapers!)
Replies: 25
Views: 13528

Re: Does i2c need pullups (resistors, not diapers!)

I believe the answer to be yes, the resistors are necessary. The Pi's SDA and SCL lines have physical resistors on the board to pull up to 3.3V. That would explain why I haven't needed them. I've only done I2C from the RPi, and they are already there. Thanks! While you don't necessarily need 10k pu...
by Richard-TX
Sun Dec 29, 2013 5:56 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO 2& 3 -> I2C, 28 & 29 -> relay control
Replies: 6
Views: 1474

Re: GPIO 2& 3 -> I2C, 28 & 29 -> relay control

Why use GPIO 28 and 29? Did you use up all the rest? If so, I would look into using a MCP23017 chip. Cost is between $1-$2 and is easy to program and use. I'd second that. I've now got two expansion boards that have that chip on them. One is the driver board for my 8x8 LED matrix. If you do use it,...
by Richard-TX
Sun Dec 29, 2013 5:48 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO 2& 3 -> I2C, 28 & 29 -> relay control
Replies: 6
Views: 1474

Re: GPIO 2& 3 -> I2C, 28 & 29 -> relay control

Why use GPIO 28 and 29?

Did you use up all the rest? If so, I would look into using a MCP23017 chip. Cost is between $1-$2 and is easy to program and use.

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