Last week we had the Athens week and we could just work at night.
We prioritize the schematic of the PCB, so I stop the software development for now to speed up the hardware.
Last week I was responsible for the minor things : Lcd, Zigbee, Spi flash memory, leds (rgb and mono), buzzer, push-buttons (with debounce in hardware) and clock.
Probably we will change the Lcd to an OLED, but I couldn’t find its documentation.
For the calculus of the clock, the Datasheet says :
pg 38 (pdf) Table 2-26 • Input Capacitance
VIN = 0, f = 1.0 MHz : 8 pF
Datasheet of MSS says :
For main oscilator: pg 121 “The recommended input capacitance is 22 pF.”
For low power oscillator : pg 123 “The recommended input capacitance is 30 pF.”
And the Evaluation Board of SmartFusion uses two 16pF capacitor for a quarts of 16pF (main oscilator), and 12pF capacitor for another quarts characterized by 12pF (low power oscilator).
So I am not sure how to calculate this capacitor, but I let this for later as we need to work in the power supply.
Power Supply :
We were going in the wrong direction but Alexis gave us a lead.
What we want to do : A battery rechargeable by USB. When the USB is connected the circuit takes the power from the USB, not from the battery.
As Gabriel said, we need provide two main sources : 9v for the motor and 3.3v for the rest, there is a 1.5v regulator inside SmartFusion, so we don’t need to worry about 1.5v.
I am working in the 3.3v power supply. I chosen the buck-boost IC LTC3113 and now I am working in its schematics.
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