Jovan Stosic
I need to create an array for time that I will use in a HTML dropdown. The array keys should be in 24 hour format and value in 12 hours with am and pm. In the database I want to store the 24h format. Is there a quick way to create the array instead of typing each hour?
Source: php – Dropdown 24 hour option values and 12 hour display – Stack Overflow
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UPDATES: (Comments,Critique to terry@yourduino.com)
Having two or more Arduinos be able to communicate with each other wirelessly over a distance opens lots of possibilities:
These are a series of low-cost 2.4 GHz Radio modules that are all based on the Nordic Semiconductor nRF24L01+ chip.
(Details) The Nordic nRF24L01+ integrates a complete 2.4GHz RF transceiver, RF synthesizer, and baseband logic including the Enhanced ShockBurst™ hardware protocol accelerator supporting a high-speed SPI interface for the application controller. The low-power short-range (50-200 feet or so)Transceiver is available on a board with Arduino interface and built-in Antenna for less than $3! There is also a high-power version (right).
Click images for details and example prices. Widely available on Ebay, Amazon too.
Below are a couple of kits with multiple nRF24L01 versions.
 |
| Low-Power nRF24L01s with Base Modules connected to YourDuino RoboREDs |
NOTE! If using the Base Module, power it from 5V not 3.3 like in these photos…
NOTE! If using the Base Module, power it from 5V not 3.3 like in these photos…
Many users have had trouble getting the nRF24L01 modules to work. Many times the problem is that the 3.3V Power to the module does not have enough current capability, or current surges cause problems. Here are suggestions:
These instability problems are particularly noticeable when 3.3V power comes from a UNO, MEGA, Nano etc. that has only 50 ma of 3.3V power available. Newer boards like the YourDuinoRoboRED have 350 ma or more available and can run even the high-power modules directly.
Range is very dependent on the situation and is much more with clear line of sight outdoors than indoors with effects of walls and materials. The usual distance quoted by different suppliers for the low-power version module with the single chip is 200 Feet or 100 Meters. This is for open spaaaaaace between units operating at a Data Rate of 250KHz. Indoors the range will be less due to walls etc… The example with radio.setPALevel(RF24_PA_LOW); will be only 10 feet or so. But reliable. You can do these things to get better range:
We suggest you test two units at your actual locations before making a decision. There are units with an Antenna Preamplifier for the receiver and transmitter power amplifier and external antenna. The range between that type unit and several low-power units will be better than between two low-power units. Every situation is a little different and difficult to get an exact number without actual tests.
Link to nRF24L01+ Data Sheet. You don’t have to, but if you want to understand more about what you can do with this “little” radio, download the data sheet. In particular you may want to read pages 7-8-9 ( For Overview and Features), and page 39 (MultiCeiver, which allows 6 Arduinos to talk to a Primary Arduino in an organized manner). Fortunately the board-level products we have take care of many of the physical and electrical details and Antenna Impedance Matching etc., and this library takes care of lots of register initialization and operational details.
There are other types of nRF24L01 modules which add Transmitter power amplifiers and Receiver preamplifiers for longer distances.. up to 1 Km (3000 feet). See them all here. These modules use an external antenna which can be a simple directly-attached one or a cable-connected antenna with more gain or directivity. Here’s what some of these look like:
Above is the low-power version, with it’s built-in zig-zag antenna. On the right you can see the pins sticking down (up in this photo) that connect to Arduino. Later we will show the pinout. NOTE!! Different Libraries use different pinouts from nRF24L01 to Arduino!!
Above is the version with Transmit Power amplifier and Receive Preamplifier. Our low-cost antenna is on the unit in the middle. The same 8 pins connect to Arduino and the base module. Same software is used. On the right is the antenna connected with a 3M cable. Connectors are “Reverse SMA”.
You might find a similar cable HERE
Here’s a link to a Home-Brew antenna design:
These transceivers use the 2.4 GHz unlicensed band like many WiFi routers, BlueTooth, some cordless phones etc. The range is 2.400 to 2.525 Ghz which is 2400 to 2525 MHz (MegaHz). The nRF24L01 channel spacing is 1 Mhz which gives 125 possible channels numbered 0 .. 124. WiFi uses most of the lower channels and we suggest using the highest 25 channels for nRF24L01 projects.
Transceivers like these both send and receive data in ‘packets’ of several bytes at a time. There is built-in error correction and resending, and it is possible to have one unit communicate with up to 6 other similar units at the same time. The RF24 Network Library extends this to multiple ‘layers’ of interconnected transceivers.
These amazing low-cost units have a lot of internal complexity but some talented people have written Arduino libraries that make them easy to us. They all use the same pinout as shown in the following diagram, which is a TOP VIEW (Correction!):
 |
| BOTTOM VIEW |
Here are details of the Pinout and connections to Arduino (updated):
The COLOR is for optional color-coded flat cable such as THIS. Photos above show an example.
NOTE: These units VCC connection must go to 3.3V not 5.0V, although the Arduino itself may run at 5.0V and the signals will be OK. The NRF24L01+ IC is a 3.3V device, but its I/O pins are 5 V tolerant , which makes it easier to interface to Arduino/YourDuino.
Arduino UNO and earlier versions have a 3.3V output that can run the low-power version of these modules (See Power Problems at the top of this page!), but the high-power versions must have a separate 3.3V supply or use a Base Module with a 3.3V regulator. The YourDuino RoboRED has a higher power 3.3V regulator and can be used to run the high-power Power Amplifier type module without a separate 3.3V regulator.
We will show an example of transmit and receive software below, and there are many examples on the RF24 Library download page. You will need a library of software to run the nRF24L01 radios. There has been a progression of improvements to the RF24 libraries by many people. TMRH20 (Who IS he/she, anyway??) has done a great job on the current library and network additions. There are lots of details but you can ignore many of them that the library will take care of.
Get TMRh20’s excellent RF24 Library that supports both Arduino and RaspberryPi:
Read about it and Download it HERE: (Click “Download ZIP” on the upper right of the page)
Read the detailed documentation HERE
Read his BLOG with advanced projects HERE
Once you have downloaded the ZIP, you should see a folder called RF24-master.ZIP. Change the name of this file to just RF24.ZIP. Double click on the ZIP and you should see a folder inside also called RF24-master. Rename this to just RF24 as well.
Then see our page about installing libraries HERE:
When you have the library installed, you can run some examples. A ways below we discuss the individual commands (methods) in the RF24 Library and show how to use them to make a simple transmit-receive system. But to get you started we suggest you start with one of the Examples in the RF24 Library from TMRh20. See this page:
https://github.com/TMRh20/RF24/tree/master/examples When you install the RF24 library, those examples are loaded on your computer. You don’t have to download them.
We suggest you start with, um, “GettingStarted”. You need to set up two arduinos, with two nRF24L01’s like in the photo above. Separate them by 5 feet or so, though. . You can run two instances of the Arduino IDE on the same machine, with two nRF24L01’s on separate USBs with separate COM#. I suggest this sequence:
RF24/examples/GettingStarted *** PRESS 'T' to begin transmitting to the other node
/****************** User Config ***************************/ /*** Set this radio as radio number 0 or 1 ***/ bool radioNumber = 1;
RF24/examples/GettingStarted *** PRESS 'T' to begin transmitting to the other node *** CHANGING TO TRANSMIT ROLE -- PRESS 'R' TO SWITCH BACK Now sending Sent 523513060, Got response 523511232, Round-trip delay 1828 microseconds Now sending Sent 524519544, Got response 524517728, Round-trip delay 1816 microseconds
And the other Serial Port window should look like:
RF24/examples/GettingStarted *** PRESS 'T' to begin transmitting to the other node Sent response 523511232 Sent response 524517728 Sent response 525521620
You can reverse the actions by type R in the transmitting side and then T in the opposite side.
OK? You can always revert to this test when things seem to stop working. NOTE: See the “POWER PROBLEMS” section above if nothing works!
You can run some other examples, but when you want to understand the RF24 library and it’s Methods better, see the section below.
See: Other Example Sketches at top of this page. Also see the very good example by Robin on THIS PAGE.
The reader will find more details and additional examples here
RF24 Library: Main Page. Download ZIP file at right
RF24 Library detailed Documentation
RF24 Library CLASS Documentation (details of a funcions and their valid parameters)
RF24 Library Examples Many examples of the capabilities of the RF24 Library
RF24 Network System A many-node Network Library
RF24 library for mesh networking A Mesh Network Library
RF24 Library for transmitting Audio
NOTE: If you wish, see ALL the details HERE.
We will try to understand the commands to set up and operate an nRF24L01 radio and build a very simple working example.
First we will look at the minimum needed to set up and transmit or receive data. Later we will write more complete examples and get them working with real radios..
EXAMPLE: (Create an instance of a radio, specifying the CE and CS pins. )
RF24 myRadio (7,8); “myRadio” is the identifier you will use in the following examples
NOTE: The following pins are fixed and unchangeable. AND Vcc (supply voltage MUST be 3.3V)
SCK to Arduino pin 13
MOSI to Arduino pin 11
MISO to Arduino pin 12
NOTE: In all following commands, you must use the same identifying name you used in the RF24 statement that created the radio. (“myRadio” in the example above) You will use that identifier followed by (dot) followed by the method (command), followed by parameters. This is “object oriented programming”. The OBJECT in this case is the Radio, and there are many METHODS that can operate on the Object. A METHOD is much like a Function or a Subroutine.
EXAMPLE: myRadio.begin(); Start up the actual radio module with the “begin” method
NOTE: “PIPES” : This is often confusing. nRF24L01 uses “pipes” that connect from transmitter to receiver. Pipes have an address you need to set. The Transmitter pipe must have the same address as the Receiver pipe. Later it’s possible to use multiple “pipes” at once
EXAMPLE OF RECEIVING DATA:
myRadio.openReadingPipe (1, const uint8_t *address) Pipe number (usually 1), pipe address (which is usually 5 bytes in an array structure).
EXAMPLE:
byte addresses[][6] = {“1Node”}; Create address for 1 pipe.
myRadio.openReadingPipe(1, addresses[0]); Use the first entry in array ‘addresses’ (Only 1 right now)
myRadio.startListening (); Turn on the receiver and listen for received data. You MUST have opened a reading pipe FIRST.
if( myRadio.available()) Check for available incoming data from transmitter
{
while (myRadio.available()) While there is data ready
{
myRadio.read( &myData, sizeof(myData) ) ; Get the data payload (You must have defined that already!)
}
myRadio.stopListening(); stop listening
EXAMPLE OF TRANSMITTING DATA:
byte addresses[][6] = {“1Node”}; Create address for 1 pipe.
myRadio.openWritingPipe(1, addresses[0]); Use the first entry in array ‘addresses’ (Only 1 right now)
myRadio.write( &myData, sizeof(myData) )
We have written working examples of Transmit and Receive sketches using these methods. See them HERE
NOTE: Many of these methods have default values you can usually use.
radio.printDetails();
Prints out a LOT of debugging information.
radio.setDataRate(RF24_250KBPS);
speed RF24_250KBPS for 250kbs, RF24_1MBPS for 1Mbps, or RF24_2MBPS for 2Mbps. 250K Bits per second gives longest range.
radio.setPALevel(RF24_PA_MAX);
Set Power Amplifier (PA) level to one of four levels: RF24_PA_MIN, RF24_PA_LOW, RF24_PA_HIGH and RF24_PA_MAX
The power levels correspond to the following output levels respectively: NRF24L01: -18dBm, -12dBm,-6dBM, and 0dBm
0 dBm is equal to 1 milliwatt. Each 3 dB is a 2:1 ratio. 6 dB is 4:1 10 dB is 10:1 So -18 dBm is 0.0000158489 watts !
To calculate all this dBm Stuff (Which us old Radio Engineers love) See THIS..
The “High Power” nRF24L01 modules like THIS have a gain of 100, so their output is +20 dBm (100 milliwatts)
radio.setChannel(108);
Which RF channel to communicate on, 0-124 Can operate on frequencies from 2.400GHz to 2.524GHz.
Programming resolution of channel frequency is 1Mhz
This is the same unlicensed band WiFi operates in (WiFi uses 2.400 to 2.500 gHz). Usually frequencies above channel 100 are best.
NOTE: In most countries the allowed frequencies are from 2.400GHz to 2.483.5GHz which you must not exceed. In USA it’s best to use channels from 70 to 80.
You can scan the channels in your environment to find a channel that is clear… See this Scanner sketch.
radio.enableDynamicPayloads();
Enable custom length payloads on the acknowledge packets. Ack payloads are a handy way to return data back to senders without manually changing the radio modes on both units.
radio.setRetries(15,15);
Set the number and delay of retries upon failed transmit. Parameters:
delay: How long to wait between each retry, in multiples of 250us, max is 15. 0 means 250us, 15 means 4000us.
count: How many retries before giving up, max 15
radio.setCRCLength(RF24_CRC_16);
length: RF24_CRC_8 for 8-bit or RF24_CRC_16 for 16-bit Cyclic Redundancy Check (Error checking)
http://www.airspayce.com/mikem/arduino/RadioHead/index.html
Another interesting example: Chat between radios:
https://github.com/stanleyseow/RF24/tree/master/examples
HERE is another good How-To example from Robin on arduino.cc
———————( COPY: Post for people having nRF24L01 Problems )———————
ALWAYS check 3.3V power. Many times intermittent operation is due to power supply regulation issues. Even though the average current may be less than 15ma, apparently there are quick transients when each transmit burst happens. The first examples in the RF24 TMRH20 library run low power and this is less of a problem.
I used to have nRF24L01 problems. Worked one day / one minute, failed the next. Now I put a 0.1uf AND 10uf capacitor right from GND to 3.3V pins on the modules, and things are MUCH better. An excellent solution is the base module shown at the top of this page.
These modules are designed to plug into a baseboard that usually has significant bypass capacitors. If you have them on the end of jumper wires you need extra bypass capacitors.
Try it and let us know here!
Jovan Stosic
Move your Linux VMs straight to containers, easily, without modifying the apps or administration processes. Canonical’s LXD is a pure-container hypervisor that runs unmodified Linux guest operating systems with VM-style operations at incredible speed and density.
Source: The LXD pure-container hypervisor | Containers | Ubuntu
Jovan Stosic
This product is not recommended for new designs. Nordic recommends the drop-in compatible nRF24L01+ or for a system-on-chip solutions the nRF24LE1 or nRF24LU1+.
Jovan Stosic
Not only can the ESP8266 connect to a WiFi network and interact with the Internet, but it can also set up a network of its own, allowing other devices to connect directly to it. This example demonstrates how to turn the ESP8266 into an access point (AP), and serve up web pages to any connected client.
Jovan Stosic
ESP8266 is a low cost wifi enabled chip. It comes in a variety of module types and can be programmed in a variety of ways.
All modules make GPIO0 and GPIO2 accessible. Most modules, other than ESP8266-01, also make GPIO15 accessible. These GPIO’s control how the module starts up and as such require special handling if they are to be used at all. GPIO6-GPIO11 also require special treatment as described below
When programming the ESP8266 using the Arduino IDE (see ESP8266-01 Wifi Shield) you sometimes (often) get an error messages in the Arduino IDE like
esp_com open failed
error: Failed to open COM33
error: espcomm_open failed
error: espcomm_upload_mem failed
In that case follow these steps to get it working:-
Check you have ESP8266 board selected in the Arduino Tools menu
Check you have selected a COM port in the Arduino Tools menu
Power cycle the ESP8266 with GPIO0 grounded (clean power application, see below)
If 3) does not fix it, unplug the USB cable from the computer wait few secs and plug it back in
If 4) does not fix it, uplug USB cable from PC, close Arduino IDE, open Arduino IDE, plug USB cable back in.
When you apply power to the ESP8266, after grounding GPIO0, make sure it is applied cleanly. Don’t jiggle the connection. The ESP8266 led should just come on and stay on without any flashes.
Most ESP8266 boards have a flash chip connected to some or all of GPIO6-GPIO11. Most programs use flash memory, as well as RAM, so unless you specifically make sure your code only runs from RAM, you can’t use these pins for other purposes.
The exact number of pins used in the range GPIO6 to GPIO11 depends on the type of flash hardware used on your module. Quad IO uses 4 lines for data (6 pins total) for up to 4 times the speed of standard. Dual IO uses 2 lines for data (4 pins total) Standard uses a single line for data ( 3 pins total).
Unless you know exactly what your board requires, you are best to just ignore GPIO6 to GPIO11 and do not refer to them from your code.
These pins determine what mode the chip starts up in.
For normal program execution GPIO0 and GPIO2 need to be pulled up to Vcc (3.3V) and GPIO15 needs to be pulled to GND, each with a resistor in the range 2K to 10K resistor. A 2K resistor gives better noise immunity. OLIMEX uses 2K resistors SparkFun uses 10K resistors. I use 3K3 resistors.
The settings of these inputs is only checked during the power up (or reset) of the chip. After that the pins are available for general use, but as discussed below their use is restricted by these external pull up/down resistors.
As noted above, these pins will already have a resistor connected to either VCC (GPIO0 and GPIO2) or GND for GPIO15. This determines how any external device, like a relay or led+resistor, must be connected. For GPIO0 and GPIO2, an external relay must be connected between VCC and the pin so that it does not interfere with the action of the pull up resistor. Conversely an external relay connected to GPIO15 must be connected between GND and the pin so that is does not interfere with the action of the pull down resistor.
To activate the external device, GPIO0 or GPIO2 must be driven LOW (Active LOW) while GPIO15 must be driven HIGH (Active HIGH).
The schematic below shows how to use GPIO0 and GPIO2 and GPIO15 as outputs. This circuit includes the necessary pullup/pulldown resistors as well. Note the 5V relay module driven by GPIO0 is opto-isolated and has a separate common connection for the input. It is important that the 5V VCCA voltage is not applied to the ESP8266 pin.
Using GPIO0, GPIO2 and GPIO15 as Inputs.
Using these pins as inputs is a bit tricky. As noted above on power up, and during reset, these pins must be pulled up or down as required to have the ESP8266 module start up in normal running mode. This means, in general, you cannot just attach an external switch to the these pins because at power up you usually cannot guarantee the switch will not be pulling the input to ground and so prevent the module from starting correctly.
The trick is to not connect the external switch directly from the GPIO0 or GPIO2 to GND but to connect it instead to another GPIO pin which is driven to ground (as an output) only after the ESP8266 starts up. Remember, when used as outputs, the GPIO pins provide a very low resistance connection to either VCC or GND depending on whether they are driven HIGH or LOW.
Here only GPIO0 and GPIO2 will be considered. Using this method you can get one (1) addition input using these two (2) GPIO’s.
A similar method can be used for GPIO15 by using another GPIO pin to connect its switch to +VCC, but this does not gain an extra input, you might as well just use the other GPIO pin directly as an input.
The circuit below uses the ESP8266-01 module as an example. Without using this trick, the ESP8266-01 does not have any free pins to use as an input if you are already using pins RX/TX for a UART connection.
Since the sketch’s
setup() method is only run after the ESP8266 module starts up, it is safe to make GPIO0 output LOW then and so provide a ground for S1 connected to GPIO2. You can then use digitalRead(2) elsewhere in your sketch to read the switch setting.This short note shows how to used GPIO0, GPIO2 and GPIO15 as outputs and how to use get an extra input using GPIO0 and GPIO2 together.
Source: Using ESP8266 GPIO0/GPIO2/GPIO15 pins
Jovan Stosic
SUSE Studio is an online Linux software creation tool by SUSE. Users can develop their own Linux OS, software appliance or virtual appliance, mainly choosing which applications and packages they want on their “custom” Linux and how it looks. Users can choose between openSUSE or SUSE Linux Enterprise as a base and pick from a variety of pre-configured images including jeOS, minimal server, GNOME and KDE desktops.
Source: SUSE Studio – Wikipedia
Jovan Stosic
I’m using Ubuntu 14.04.1 server. Recently, I installed Ubuntu desktop for it; before that it had automatically gained an IP address through DHCP. After installing Ubuntu desktop, I have provided an IP address as static but it is not obtaining that IP address. Instead, it is showing the DHCP address. When I check connection information, it is showing me the error message, “Error displaying connection information, no valid active connection found.” I tried with ifconfig command but it shows the IP address as gained by DHCP but not the static one which I gave so I can browse the internet. I need to provide a static IP address. I have uploaded the error image. Please help me.
Jovan Stosic
NodeMCU is an open source IoT platform.[4][5] It includes firmware which runs on the ESP8266 Wi-Fi SoC from Espressif Systems, and hardware[6] which is based on the ESP-12 module. The term “NodeMCU” by default refers to the firmware rather than the dev kits. The firmware uses the Lua scripting language. It is based on the eLua project, and built on the Espressif Non-OS SDK for ESP8266. It uses many open source projects, such as lua-cjson,[7] and spiffs.[8]
Source: NodeMCU – Wikipedia
Jovan Stosic
This comparison of ESP8266 NodeMCU development boards also includes a comparison of ESP8266 chips used on those boards. The names can be confusing.
Source: Comparison of ESP8266 NodeMCU development boards • my2cents
Jovan Stosic
ESP8266 core for Arduino
Jovan Stosic
Description: An Arduino UNO Compatible wifi board based on ESP8266EX.
Features:
Tutorial:
| Microcontroller | ESP-8266EX |
| Operating Voltage | 3.3V |
| Digital I/O Pins | 11 |
| Analog Input Pins | 1(Max input: 3.2V) |
| Clock Speed | 80MHz/160MHz |
| Flash | 4M bytes |
| Length | 68.6mm |
| Width | 53.4mm |
| Weight | 25g |
| Pin | Function | ESP-8266 Pin |
| TX | TXD | TXD |
| RX | RXD | RXD |
| A0 | Analog input, max 3.3V input | A0 |
| D0 | IO | GPIO16 |
| D1 | IO, SCL | GPIO5 |
| D2 | IO, SDA | GPIO4 |
| D3 | IO, 10k Pull-up | GPIO0 |
| D4 | IO, 10k Pull-up, BUILTIN_LED | GPIO2 |
| D5 | IO, SCK | GPIO14 |
| D6 | IO, MISO | GPIO12 |
| D7 | IO, MOSI | GPIO13 |
| D8 | IO, 10k Pull-down, SS | GPIO15 |
| G | Ground | GND |
| 5V | 5V | – |
| 3V3 | 3.3V | 3.3V |
| RST | Reset | RST |
Source: D1 | WEMOS Electronics
