New module: POT board
#1
Hi all,

Very cool to see the new modules being talked about and shown.

I saw the latest Kickstarter update and was wondering what the role of the "12C POT board" was? What is this and what would it be used for? Or is this one of those "if you have to ask then it isn't for you"-type scenarios?  Smile

Cool
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#2
(01-30-2016, 07:30 PM)Crispin Wrote: Hi all,

Very cool to see the new modules being talked about and shown.

I saw the latest Kickstarter update and was wondering what the role of the "12C POT board" was? What is this and what would it be used for? Or is this one of those "if you have to ask then it isn't for you"-type scenarios?  Smile

Cool

I'm not really sure, either...I do know that I²C stands for Inter-Integrated Circuit 

https://en.wikipedia.org/wiki/I%C2%B2C

Apparently, 'It is typically used for attaching lower-speed peripheral ICs to processors and microcontrollers.'

There's a page on the Pine A64 wiki about it and the various other POTs:

http://wiki.pine64.org/index.php/POT#POT...PMI2C01.29

Simply put, it's for connecting stuff to. 

Someone will hopefully come along in a while and fill in some more specifics and examples of how the I²C  POT board might be used...

Welcome to the forum Big Grin
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#3
It is a board to plug in module boards that have a I2C interface. Many devices such as sensors like temperature, humidity, pressure, acceleration, etc, have I2C interfaces to make it easy to connect multiple devices to a singe serial interface. Companies such as Adafruit and Sparkfun sell breakout boards for devices that use I2C interfaces and while they are not designed to work with the POT board, they can give you an idea of the uses for them.
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#4
For the temperature and humidity sensors, what's the accuracy with them? I have a big need for accurate temp and humidity sensors that can transmit data back to a host computer (preferably over wifi), but the temp sensor needs to be a probe that can accurately read ice temperature to 0.1F
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#5
Aha - thanks, guys. I was mis-led by the caption of the pic in the update being "12C" (and the device actually *having* 12 connectors on it!) and I wasn't familiar enough with "I2C" to recognise it.

So this board is likely to be a pre-requisite for the humidity, temp, etc, sensors? And the most likely application would be the OpenHAB home automation setup?

So much potential for these little boards!
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#6
What I don't like - is it is yet an other damn connector type.

There is a pretty decent type of connector that is well defined  (PMODS)
you an buy all kinds of little gadgets and connect them

For example:

http://store.digilentinc.com/pmod-peripheral-modules/

And  https://www.maximintegrated.com/en/desig...dules.html

Why did you use yet another type of connector?

-Duane.
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#7
Well the normal 0.1" connector used by the larger buses (pi and euler in the case of pine64) are ok when you have a number of pins, but when you get down to 4 and 5 pin connections, have an annoying tendency to come apart. So they used a locking connector that makes it harder for the connection to come apart by accident. For sensors that may be in remote things that is probably a reasonable decision. From the photo, it looks like it may be one of the standard (JST?) connectors. If you are not worried about the cables coming out when you yank on them, I assume that a normal 4 pin 0.1" female header will fit inside of the locking connector.

However, there is a disconnect in their i2c designs. The normal i2c connection has 4 pins (ground, power, scl, sda) and most of the plugs have 4 pins. But the ambient light sensor wants to pass a 5th pin (called nInt, which presumably is a pin that goes high when the state changes so that you can attach an interrupt so that you know when their is new data). They put the nInt pin between ground and sda pins, which means you can't intermix 4 pin and 5 pin i2c connections.

As to what i2c is, it is a slow speed shared bus that you can attach simple devices to it (up to about a 100 or typically less). Each slave device has an address (much like a telephone) and the master builds a packet that has the address in it, and the slave devices will only respond if the address matches their configured address. On a given i2c bus, each address must be unique. Depending on the device, there might be switches or solder jumpers to change the address, or some devices have an i2c command to change their address.

Note, without using extenders, etc. the i2c bus is fairly limited, and the total length of all wires should be under a few meters.

The board is mis-named (IMHO). From the title, it sounds like a board that can directly hook up 12 potentiometers (variable resisters like analog dials), but instead it is a shared i2c bus board. Yes, you can hook up 12 i2c devices, each of which provides a potentiometer and has a small microprocessor to do the i2c connection, but you can also hook up displays, switches, etc.

I don't know if the Linux and Android OSes can enable higher speed i2c buses. The last time I checked, the Raspberry Pi could only do the slowest i2c speed (100kHz).
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#8
(01-30-2016, 11:00 PM)CanadianIceTech Wrote: For the temperature and humidity sensors, what's the accuracy with them? I have a big need for accurate temp and humidity sensors that can transmit data back to a host computer (preferably over wifi), but the temp sensor needs to be a probe that can accurately read ice temperature to 0.1F
I think I found the board you are looking for:
http://wiki.pine64.org/index.php/POT#WiF...PMWF01A.29

And there is a temperature and humidity sensor plugin:
http://wiki.pine64.org/index.php/POT#I2C...PMSDP01.29

However there is no temperature probe or any one that I know of that has a I2C interface. Adafruit sells a temperature probe that is designed to be directly interfaced to a computer that I think has the accuracy you need:
https://www.adafruit.com/products/381

I do not know if it can be interfaced to the WiFi remote board.
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#9
(01-31-2016, 11:42 AM)stephen fleming Wrote:
(01-30-2016, 11:00 PM)CanadianIceTech Wrote: For the temperature and humidity sensors, what's the accuracy with them? I have a big need for accurate temp and humidity sensors that can transmit data back to a host computer (preferably over wifi), but the temp sensor needs to be a probe that can accurately read ice temperature to 0.1F
I think I found the board you are looking for:
http://wiki.pine64.org/index.php/POT#WiF...PMWF01A.29

And there is a temperature and humidity sensor plugin:
http://wiki.pine64.org/index.php/POT#I2C...PMSDP01.29

However there is no temperature probe or any one that I know of that has a I2C interface. Adafruit sells a temperature probe that is designed to be directly interfaced to a computer that I think has the accuracy you need:
https://www.adafruit.com/products/381

I do not know if it can be interfaced to the WiFi remote board.
I think that is probably what I'm looking for. If I can use a $15 pine64 board in a case that has a large battery (to lengthen times between charging), plus the sensors it'd be far cheaper than what is commercially available. Ideally I'd like to have a wifi receiver on the outside of my office to collect the data from the sensors, then send to a laptop. This will be for monitoring, and also for remote alerts of warm temps caused by a power plant failure so I can try and save the ice while the issue is resolved with the ice plant. (http://www.eyeontheice.com/index.html)

I'm assuming this would be a good humidity sensor? https://www.adafruit.com/products/1293
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#10
(01-31-2016, 03:59 PM)CanadianIceTech Wrote:
(01-31-2016, 11:42 AM)stephen fleming Wrote:
(01-30-2016, 11:00 PM)CanadianIceTech Wrote: For the temperature and humidity sensors, what's the accuracy with them? I have a big need for accurate temp and humidity sensors that can transmit data back to a host computer (preferably over wifi), but the temp sensor needs to be a probe that can accurately read ice temperature to 0.1F
I think I found the board you are looking for:
http://wiki.pine64.org/index.php/POT#WiF...PMWF01A.29

And there is a temperature and humidity sensor plugin:
http://wiki.pine64.org/index.php/POT#I2C...PMSDP01.29

However there is no temperature probe or any one that I know of that has a I2C interface. Adafruit sells a temperature probe that is designed to be directly interfaced to a computer that I think has the accuracy you need:
https://www.adafruit.com/products/381

I do not know if it can be interfaced to the WiFi remote board.
I think that is probably what I'm looking for. If I can use a $15 pine64 board in a case that has a large battery (to lengthen times between charging), plus the sensors it'd be far cheaper than what is commercially available. Ideally I'd like to have a wifi receiver on the outside of my office to collect the data from the sensors, then send to a laptop. This will be for monitoring, and also for remote alerts of warm temps caused by a power plant failure so I can try and save the ice while the issue is resolved with the ice plant. (http://www.eyeontheice.com/index.html)

I'm assuming this would be a good humidity sensor? https://www.adafruit.com/products/1293
More detail info and sensor/IC spec for board can be found at,

http://wiki.pine64.org/index.php/POT

For the I2C 4 wire connector, the pin are GND,SDA,SCL and 5V. For the five pin are GND, INTR, SDA, SCL and 5V. For some of the I2C device, they are build in with interrupt. With this interrupt, the CPU will have faster reaction time when certain condition is trigger. This also implied that if the CPU is waiting for the trigger condition, the CPU do not need to scan I2C device thus provide a more efficient use of I2C bus. 6 connectors ( 2pcs five pin and 4pcs of four pin I2C connector) is connect to TWI1-SCL/SDA channel in the pi-2 bus and another 6pcs of the connector is connected to TWI-SCL/SCA channel in the Pi-2 Bus.

All of the INTR pin for the total of 4pcs of connector is connected to separate GPIO of the bus indicating on the PCB.

Both of the I2C channel is going through a I2C Bus Repeater ( PCA9517)  before connecting out to the connector. This will allow the I2C bus to run either in 5V I2C bus or 3.3V I2C bus.

The idea is that you can make use of the PineA64 as sensor Hub and all the sensor is connected to the PineA64 board. For longer distance that which you do not want to pull a long cable, you can make use of the Wifi Remote I2C ( http://wiki.pine64.org/index.php/POT#WiF...PMWF01A.29 ) to use a remote I2C repeater. The I2C connector on the board has the same I2C pin layout configuration. Furthermore, Wifi Remote I2C has a on board relay that allow for 240Vac on/off. the Currently we are still developing the firmware for the Wifi Remote I2C. Once it is ready, we will publish the source for the firmware.

On Humidity and Temperature Sensor, it is base on Silicon Lab Si7021. The sensor IC is mounted on the reverse side of the board. In term of accuracy, it is consider quite good, please refer to  spec the for the detail. The only downside for this IC is that it do not have any address selector and only allow 1 sensor per I2C channel. But if more sensors need to be install, you can make use of the Wifi Remote I2C to allow more Humidity and Temperature Sensor to be installed.

As for the Ambient Light Sensor  it is base on TSL2561T from AMS. The reason for the 5 pin I2C connector is that this sensor allow the CPU to configure a trigger point base on the received light intensity. Once it reaches the level, it will provide a trigger to the CPU.

../KH Goh
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