Vermes
Advanced Member level 4
Main features ans assumptions:
- low current consumption (portably, battery powered)
- fits a hand
- support only through the touch screen
- graphic display 240x128 T6963
- flashlight
- GSM module
- Bluetooth module
- GPS included
- accelerometer LIS35DE
- RTC DS1307
- AT keyboard support
- SD cards support by AVRDOS
- RS232/485 communication (when RS232, adjusting the jumper if the output signal should be TTL or converted by MAX232)
- measurement of current consumed
- measurement of voltage on the power
- measurement of voltage 0-50V
- thermometer
- regulated LCD backlight
- UART divided in four devices on AND gates (74HC08) (because in Atmega128 there are only two incorporated UART channels and in this device four elements need data)
PALM was divided into parts 5V and 3V3. Processor was powered by voltage 5V and those system accept signals on level of 3V. So the voltage that is sent by the processor to the peripheral chips on resistors 1k6 and 3k8, should be lowered.
Some of the transmitter/receiver channels did not function properly.
Bluetooth module was connected with a mobile phone and receive commands from a computer.
The accelerometer wasn't soldered yet, when there was a serious collision on transmission of 5V system DS1307 and 3V sensor of acceleration. The choice was between accelerator and clock. The clock seems better, because there is no need to drag the wires over the system.
To receive information about the current consumption, two resistors 1R in 1206 housings linked parallel. They were placed on the mass of the momentary current 1A gave a drop about 0,5V, which was let on the ADC channel. That wasn't working too well, so the differential channel of transducer should be used, lower values of resistance and set the gain at 20x.
Operation firstly was planned to be based on a touch screen, but it turned out impossible.
Components to the transition from the thermal transfer method for making PCBs to photochemical technology.
New thermal transfer paper was used. After ironing the print, the quality and speed of the transfer in comparison to photochemical method, were excellent. Paths were not so nice, and one 0,1mm was not seen under the accelerometer, but the rest was ok.
The plate was designed in Eagle program, it has two layers. The project was time consuming and connecting the paths were quite tedious.
A positive accent was activating AVRDOS.
The current consumption was more than was in assumptions, in the least active moment it was about 100mA. Probably the reason was using linear voltage stabilizers.
Link to original thread – PALM v1.0 BETA Atmega128