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by pjr_pdco
Fri Jan 08, 2016 6:50 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: i2c interface detect anything [SOLVED]
Replies: 37
Views: 5516

Re: i2c interface detect anything [SOLVED]

Possibly the Arduino can function as both master and slave. See these:

https://www.arduino.cc/en/Tutorial/MasterReader
https://www.arduino.cc/en/Tutorial/MasterWriter

Combine the two functions ( Wire.onReceive and Wire.onRequest ) into a single application to handle the slave operation.

Pat
by pjr_pdco
Wed Jun 24, 2015 4:24 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Sense float voltage vs batt voltage
Replies: 8
Views: 1053

Re: Sense float voltage vs batt voltage

"When running on the float charger" to me means the AC ( mains ) supply is available and with "running on battery" the AC(mains) is not available. Why not sense that? Maybe just use output from a 3.3v wall wart power supply to an I/O pin with a resistor to 0v ( and connect the power supply 0v to the...
by pjr_pdco
Fri May 15, 2015 2:46 pm
Forum: Automation, sensing and robotics
Topic: Pond Depth!
Replies: 17
Views: 3961

Re: Pond Depth!

Consider the bubbler method. It is simple and the only thing in the water is a (plastic)tube.

Pat
by pjr_pdco
Sat May 02, 2015 3:49 am
Forum: Automation, sensing and robotics
Topic: MAX31865 PT1000 temperature measurement over long distance
Replies: 27
Views: 18338

Re: MAX31865 PT1000 temperature measurement over long distan

The component datasheet is a great place to start. I have not worked directly with the MAX31865 so what follows is just from reading the datasheet. In the original post it looks to me the chip was actually working correctly. Communication with the chip is through a register set with addresses of 0x0...
by pjr_pdco
Sun Mar 22, 2015 3:44 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 20x4 RGB LCD via GPIO and current draw
Replies: 1
Views: 860

Re: 20x4 RGB LCD via GPIO and current draw

It is difficult to make anything more than general comments without knowledge of the specific hardware in use. I mean the connection you are using between the Pi & the display and about the display itself. Given the parameters you list and assuming the display is connected directly to the PI without...
by pjr_pdco
Wed Feb 25, 2015 1:18 am
Forum: Automation, sensing and robotics
Topic: Servos on I2C at start up
Replies: 3
Views: 891

Re: Servos on I2C at start up

My guess would be when the Pi starts running & generating the servo signals it defaults to the pulse width which positions a servo to its middle of travel. Perhaps what is needed is to retain the last servo position value in some form of non-volatile memory and have the servo power controlled by the...
by pjr_pdco
Fri Feb 20, 2015 2:03 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Bright Pi I2C 5 volt and 3 volt
Replies: 4
Views: 1476

Re: Bright Pi I2C 5 volt and 3 volt

From a review of the datasheet for the Semtech SC620 it looks to me it would be OK to power the BrightPi from 5v and connect the SDA & SCL to the Pi I2C port ( connect the SC620 & Pi GND also ). A device operation from 5v does not also mean/require the I2C bus pins are operating at 5V too. The I2C b...
by pjr_pdco
Wed Jan 21, 2015 5:51 pm
Forum: Automation, sensing and robotics
Topic: Thermal camera
Replies: 46
Views: 66877

Re: Thermal camera

Panasonic has a part named Grid Eye. It has 8x8 elements, i2c and about $30US.
by pjr_pdco
Thu Jan 15, 2015 6:12 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Breadboard-friendly logic level shifters with strong out
Replies: 7
Views: 3520

Re: Breadboard-friendly logic level shifters with strong out

For beginners, dealing with transistors with their npn/pnp pinouts might be a bit tricky [Getting onto soapbox] Don't shy away from something not understood. Embrace it, learn it, master it! [off of the soapbox now..] That philosophy drives my grandson's crazy while helping them with homework. Anyw...
by pjr_pdco
Wed Jan 14, 2015 4:11 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Breadboard-friendly logic level shifters with strong out
Replies: 7
Views: 3520

Re: Breadboard-friendly logic level shifters with strong out

Adafruit has the 74AHCT125 ( http://www.adafruit.com/product/1787 ) in stock. There are simple methods to accomplish the level shift. You say you do not want to "fiddle" with low level components however nothing would be much simpler than a couple transistors & resistors to do it. this would invert ...
by pjr_pdco
Wed Jan 14, 2015 3:38 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: DAC + LCD-PI43 connection
Replies: 3
Views: 1028

Re: DAC + LCD-PI43 connection

It is a bit difficult to say for sure. Obviously you will need some method to share the GPIO connector. Then what are the GPIO requirements for each product. The LCD-Pi43 states needing SPI & 1 GPIO. I do not find on the DAC site any direct statement about what I/O is needed. You must add J5 to the ...
by pjr_pdco
Wed Jan 14, 2015 3:11 am
Forum: Automation, sensing and robotics
Topic: Addressable 12vdc pumps and valves
Replies: 7
Views: 2001

Re: Addressable 12vdc pumps and valves

An aspect or you system not mentioned is its layout. Are you thinking something with the nodes close together or more distributed ( a few meters or more between nodes )? This is important to consider when deciding the bus electrical interface. While there are methods to implement a 1Wire bus of some...
by pjr_pdco
Mon Jan 12, 2015 5:57 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Fixed I2C address - best solution for third sensor
Replies: 41
Views: 6707

Re: Fixed I2C address - best solution for third sensor

The diagram shows pull-ups to 5V on the port pins. This probably violates the maximum voltage input electrical specification for the pins. I have not been able to view a datasheet for the Broadcom part however I would guess the spec. is something like VDD +0.3V. The reason it "works" is the high val...
by pjr_pdco
Sun Jan 11, 2015 6:46 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Control a 8*8 LCD bicolor led matrix
Replies: 2
Views: 695

Re: Control a 8*8 LCD bicolor led matrix

Is the display working for you now? If so check what I have written below to see if I got close to correct. If not below is my guess about this. It comes from review of the component datasheet & the code. I have not worked with either directly. It looks like the second parameter specifies the displa...
by pjr_pdco
Fri Jan 09, 2015 9:38 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Fixed I2C address - best solution for third sensor
Replies: 41
Views: 6707

Re: Fixed I2C address - best solution for third sensor

In the PCA9544 data sheet, figure 14 on page 12 gives a good diagram. The pull-up resistors on the bus master side can be removed sice the RPi already has them. Also the schematic for the DSS Circuits breakout pcb shows pull-up resistors are included for the interrupt lines. Just solder a jumpers on...
by pjr_pdco
Fri Jan 09, 2015 7:55 pm
Forum: Automation, sensing and robotics
Topic: Piggy backing on a normal doorbell
Replies: 7
Views: 2226

Re: Piggy backing on a normal doorbell

That 50ma is the specified absolute maximum input current. Something like 15 - 20 ma is more reasonable. Also note the output of the phototransistor will be pulsing at the line frequency ( 50Hz in this case I think ). The mains line sine wave will alternately turn on one of the diodes. When at zero ...
by pjr_pdco
Thu Jan 08, 2015 6:53 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Fixed I2C address - best solution for third sensor
Replies: 41
Views: 6707

Re: Fixed I2C address - best solution for third sensor

About the PCA9544A interrupt inputs: Also second Q, in the spec it says "The interrupt inputs should not be left floating.", given that I don't want to use that, I assume it doesn't matter? The component spec sheet states: If unused, interrupt input(s) must be connected to VDD through a pull-up resi...

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