In many microcontroller projects you need some non-volatile memory – which preserves data even when power is off. Most popular type of such memory is Flash or EEPROM. Many MCUs like AVR or PIC already have some EEPROM inside chip that may suite your needs. But in many cases it is not included and you may need to connect it externally. EEPROMs with I2C interface is very common in such situation as they don’t need lots of I/Os (only two wires). If you decided to add an EEPROM chip in to your project check out the useful guide on how it works written by Jesus Echavarria. As example he took 24LC256 EEPROM which capacity is 32K x 8 bytes. Chip works in pretty wide voltage range – between 1.7V and 5.5V which is great either for 3.3V or 5V setups.
He covers all the basic things you need to take care of including selecting proper chip slave address in I2C line. Then performing reading and writing EEPROM data in byte and page modes. This guide might serve as nice snippet for your next project so you don’t have to scratch head if something goes wrong.
I2C interface allows connecting multiple devices using two wires. This interface is very popular in sensors, memory chips and IO expanders. R-B designed compact breakout board where he placed MCP9802 temperature sensor and 24LC512 EEPROM.
Module is convenient to use as temperature sensor with ability to log values in to near by memory. So if you decide to unplug sensor – history of data goes with you. 512Kbit EEPROM gives enough space for storing data. Digital temperature sensor is capable of measuring temperatures from -55ºC to 125ºC. Prototyping board is designed so it could be easily plugged in to prototyping breadboard.
Any AVR microcontroller is an 8 bit computer in a chip designed and manufactured by ATMEL Corporation. It has some RAM memory and ROM (Flash) as well. To make things more attractive and useful there is also an EEPROM memory. Including AVR core CPU all these are more than enough to say that it is a small computer where you can execute programs stored in Flash memory, run them while operating data in SRAM and storing some constant values in EEPROM. Comparing to real computer that sits on your table you can say that AVR core is a CPU like AMD or Pentium. Flash memory would be your hard drive where programs are stored, RAM is RAM nothing to add there. EEPROM probably can be compared to some media device like CDRW. Anyway this is only similitude in different scale.
AVR microcontrollers aren’t limited with core CPU and memory. The main thing what makes them valuable (and any other type of microcontroller) – they are rich in peripherals inside chip. In most cases you will find USART, I2C, SPI, ADC, Timers/Counters, and bunch of I/O pins. Single chip alone already can to do massive work. I believe there is no need to go more in details about more specific details of AVR microcontrollers as these can be found in datasheets. Continue reading
Did anyone here ever get in touch with the GSM call alarm or GSM SMS alarm before? If you did, then the Tiny GSM alarm system is going to be the masterpiece combination of the call alarm and SMS alarm!
The main purpose of the tiny GSM alarm system is a device, which is can be used to operate standalone or as a module for existing alarm system. The tiny GSM alarm system is much more advanced than the previous, as it’s not only can arm or disarm the system with “enable” pin, but you can do the same task by simply calling from your own phone! Sounds like a cool add-on, isn’t it?
Well, the tiny GSM alarm system is built on a very popular microcontroller, the PIC16F84A. In this case, you don’t have to bother with external EEPROM memory for SMS storage, as you have the option to use phone’s SIM SMS storage and phonebook memory for the storage task!
Well, the GSM phone that is best compatible with the device is Siemens M35i. To be honest, it’s better to modify the phone first, so that it can be easily powered and turned on by the device. Furthermore, you should make sure that the SIM PIN code request are disabled, as you don’t want to be bothered by it, especially when you’re dealing with the wiring and coding processes!