EE459 Group 3 SAMSUNG SAGE Jacob Jensen Michael Grotelueschen Garlan Khachatourian Garlan – Current Sensor / ADC, seven segment, Relays, Building the circuitry, Schematics Jacob – Intro, Programming the Base, Wireless, RTC Michael – Programming the Remote, Buttons, LCD, EEPROMThe Task The Samsung Sage is a professional, home-orientated, power-saving device. We strived to create a feature-rich device that was also ascetically pleasing and still saved a lot of power. The Sage is ideal for powering computer workstations or home theater setups. Computers and other media devices such as televisions are the biggest power “vampires.” Overview of Features Individually Programmable Outlets Our product has four individually programmable power outlets. There are cases in which a user may want some sockets on, and others off. For example, they may leave their computer on standby when away from home. They don’t want power to be disconnected from the computer or else data will be lost. However, peripherals such as the monitor, speakers or external hard drives can be disconnected from power. Each outlet has an LED next to it to show whether the outlet is on or off. These LEDs are also used to inform the user that a wireless signal has been accurately received. Wireless Remote Realizing that power strips of this nature are usually positioned out of sight behind desks or TV stands; we deemed it appropriate for our device to have an all-encompassing wireless feature. Such a feature would provide users with total control of the device from range. Our solution to this challenge was the creation of a RF wireless remote which housed the primary input-output system. In order to conserve battery power on the remote, wireless data only needs to be sent after an update to the schedule. After receiving a wireless encoding of the schedule, the base module can run independently of the remote. During these periods, the remote can be turned off entirely for prolonged battery life. Input/Output The primary I/O of the Sage lies on the wireless remote. A 20x2 character LCD displays information to the user, and input is driven through six buttons. Four of these buttons are arranged in a diamond shape, providing typical left-right-up-down menu control. The two additional buttons are for initiating transfer of schedule data over the wireless link and to send an “override” signal. Components The Concept for Samsung SageWireless RF Link RF Link Transmitter – 315 MHz, Sparkfun, Part # WRL-08945 RF Link 2400bps Receiver - 315MHz, Sparkfun, Part # WRL-08948 Achieving a reliable wireless connection with this particular hardware was perhaps the most difficult task of this prototype. Data is transmitted serially over the RF connection at 2400 or 4800 baud. We used 4800 baud, finding that even short periods of inactivity on the RF link would inevitably cause noise and junk data on the receiver. Initially the transmitter was powered by the common 5V source. However, we eventually wired the transmitter directly to the 9V battery to improve the signal. These RF devices can handle source voltages of up to 12V. We also eventually placed a 23cm antenna on the transmitter as recommended by the data sheet. The increased voltage and antenna greatly improved the range and reliability of the link. The transmitter data pin is connected directly to the SCI transmit pin of the uC on the remote. Likewise, the receiver data pin is connected directly to the SCI receive pin of the uC on the base. The SCI protocol made it easier to send byte-sized chunks. What we needed to send over the RF link was time data compatible with the RTC. This amounts to seven bytes. An entire packet is made up of one command byte, the seven data bytes, an arbitrary byte, and a checksum byte for a total of 10 bytes per packet. See Figure 1 for a visual representation of this sequence. There are 5 types of command bytes. They are listed here: 0xFF – Set the RTC time 0x99 – Start 0x55 – Stop 0xAA – Override 0x00-0x37 – Write directly to that location in memory. Updates a specific on/off time for a certain socket on a certain day. Start and stop commands are used when sending multiple packets. When only sending a single packet, i.e. setting the RTC time or an override, it is not necessary to use start or stop commands. When using start and stop commands, the rest of the packet is ignored, although the checksum must still be correct and the arbitrary byte 0x55 must still be present. A visual representation of the RF LinkWhen sending schedule data over the RF link all data should be sent in a single burst. This allows all data in the base module to be refreshed in case it becomes corrupted or outdated. Additionally, if a user needs to retransmit data for any reason, they do not need to remember which data needs to be sent. Real Time Clock – Maxim DS1307 The RTC is wired to the uC through the I2C interface with external pull-up resistors. There is nothing exceptional about our use of the RTC other than we used its data structure as the basis for all our scheduling data. Initially, we intended to use the RTC’s built-in memory to store our scheduling data. We realized a little later that this extra memory was too small for what we had in mind. Below is the memory layout of the RTC. Buttons Buttons are included in the design to receive user inputs. There are six total buttons; four are dedicated to time setting and scheduling input and directional movement throughout the menu, while the remaining two control various functions. While viewing the set time menu, the upper left input allows the user to stop the clock for setting and then restarts the clock; in the schedule menu, this input allows the user to program the base with the current schedule. The upper right button takes the user from one menu to the other, although if this button is held while the upper left button is pressed, the schedule programmed into the base is ignored. LCD – Matrix Orbital MOP-AL202C-BFTW The display is a 2 x 20 character white-on-blue LCD. The duty of the LCD is to communicate useful information to the user. The approach to the actual display of information on the LCD is minimalist. The set time menu displays the time and day according to the clock. The schedule menu has two parts; part one displays the plug
View Full Document