Pcomp notes: Wireless communication
- complex data communications
- configuration vs. communication (command move vs. data mode)
- addressing
- Bluetooth serial as example
- protocols discussion
- Optional Bluetooth Lab or TBA depending on class topics
why isn’t everything wireless? there’s no one-to-one network
they need power
one on one exchanges of information through infrared light
turn your emitter on or off to give it pulses
Electromagnetic induction is the production of an electric current across a conductor moving through a magnetic field. It underlies the operation of generators, transformers, induction motors, electric motors, synchronous motors, and solenoids.
Radio-frequency identification (RFID) is the use of a wireless non-contact system that uses radio-frequency electromagnetic fields to transfer data from a tag attached to an object, for the purposes of automatic identification and tracking. Some tags require no battery and are powered and read at short ranges via magnetic fields (electromagnetic induction). Others use a local power source and emit radio waves (electromagnetic radiation at radio frequencies). The tag contains electronically stored information which can be read from up to several meters (yards) away. Unlike a bar code, the tag does not need to be within line of sight of the reader and may be embedded in the tracked object.
Modem:
A modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from light emitting diodes to radio. The most familiar example is a voice band modem that turns the digital data of a personal computer into modulated electrical signals in the voice frequency range of a telephone channel. These signals can be transmitted over telephone lines and demodulated by another modem at the receiver side to recover the digital data.
Bluetooth:
a little more power consuming, a high frequency radio transmission. developed for mobile phones to transmit large files. Bluetooth works by pairing devices and they will ignore any other device on that network.
ZigBee is a specification for a suite of high level communication protocols using small, low-power digital radios based on an IEEE 802 standard for personal area networks. ZigBee devices are often used in mesh network form to transmit data over longer distances, passing data through intermediate devices to reach more distant ones. This allows ZigBee networks to be formed ad-hoc, with no centralized control or high-power transmitter/receiver able to reach all of the devices. Any ZigBee device can be tasked with running the network.
AT Hayes commands:
When it is in command mode. When it is in data mode it’s ignoring you, acting s a bridge.
1. data mode in which the modem sends the data to the remote modem. (A modem in data mode treats everything it receives from the computer as data and sends it across the phone line).
2. command mode in which data is interpreted as commands to the local modem (commands that the local modem should execute).
To switch from data mode to command mode, sessions sent an escape sequence string of three plus signs (“+++”) followed by a pause of about a second. The pause at the end of the escape sequence was required to reduce the problem caused by in-band signaling: if any other data was received within one second of the three plus signs, it was not the escape sequence and would be sent as data. To switch back they sent the online command, O. In actual use many of the commands automatically switched to the online mode after completion, and it is rare for a user to use the online command explicitly.
In computer telecommunication, the Hayes command set is a specific command-language originally developed for the Hayes Smartmodem 300 baud modem in 1981. The command set consists of a series of short text strings which combine together to produce complete commands for operations such as dialing, hanging up, and changing the parameters of the connection. The vast majority of dialup modems use the Hayes command set in numerous variations.
int fsrPin =A0;
int val =0;
void setup () {
Serial.begin (115200);
}
void loop () {
val = analogRead (fsrPin);
int hue = map (val, 0, 100, 0, 255);
Serial.println(hue);
delay(20);
}
go to serial port processing sketch
XBee is the brand name from Digi International for a family of form factor compatible radio modules. The first XBee radios were introduced under the MaxStream brand in 2005[2] and were based on the 802.15.4-2003 standard designed for point-to-point and point-to-multipoint communications at over-the-air baud rates of 250 kbit/s.[3]
Homemade cellphone module
Need an antanee and sim card
