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96 lines
3.3 KiB
Markdown
96 lines
3.3 KiB
Markdown
# Easyduino Arduino
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The Microcontroller that propelled the Maker and Hobbyst movements
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<p align="center">
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<img src="https://github.com/Hanqaqa/Easyduino/blob/master/Atmega328p%20Arduino%20Uno/ProductionFiles/Photos/Easyduino%20UNO%20Iso.jpg" width="60%">
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</p>
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## Schematic
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<p align="center">
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<img src="https://github.com/Hanqaqa/Easyduino/blob/master/Atmega328p%20Arduino%20Uno/ProductionFiles/PDFs/Schematic_Page_1.png" width="60%">
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</p>
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## Gerbers
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<p align="center">
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<img src="https://github.com/Hanqaqa/Easyduino/blob/master/Atmega328p%20Arduino%20Uno/ProductionFiles/PDFs/Gerbers.png" width="60%">
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</p>
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## Specs
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- Input Voltage: 6.5V-15V(External Source Vin) 5V (USB). Both can be used at the same time.
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- 5V Output Current: 1A (External Source) 500mA (USB)
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- 3.3V Output Current: 500mA (External Source) 250 mA (USB)
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- Polarity Protection (External Source) diode D2
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- Overcurrent Protection: None (External Source) 1A (USB)
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- 5V Autoselector: can take both USB and external source. A diode will avoid short circuit
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- External Input Polarity protection: A diode will protect the circuit from a wrongly inserted battery.
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## References
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### Atmega 328p
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#### Reset
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- Atmega Hardware Design Considerations p7,p8 -> 10kR, 100nF cap and 330R for switch. The 100nF is not used in Arduino (produces erors with DTR)
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- The 100nF capacitor on DTR (CH340C) is used for tricking Arduino into Bootloader mode, it produces a voltage spike.
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#### Crystal
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- Atmega Hardware Design Considerations p16 -> 22pf
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#### AVCC
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- Atmega328 Reference Manual p213 -> 10uH ferrite bead and 100nF
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- The Analog tracks aren't critical. I won't create an analog ground for these tracks
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#### ICSP Connector
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- Atmega Hardware Design Considerations p12
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#### AREF
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- Atmega Hardware Design Considerations p6 -> 100nF
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### USB-C
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#### Filtering
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- USB Hardware Design Guidelines for FTDI ICs p8 -> 10nF Cap + Ferrite Bead + 100nF Cap + 4.7uF Cap
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- I disregarded such heavy filtering for the easier to implement 1uF and 100nF cap given in the CP2102 datasheet
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- I added a polyfuse with Ihold=500mA and Itrip=1A.
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#### Differential Pair
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- USB needs 90 Ohm differential traces.
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- According to JLCPCB impedance calculator, with a JLC7628 prepreg and 6mil (0.15mm) space between lines
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- I have to use 9 mil tracks -> 0.2 mm
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- I will use a very short trace for D+ D- (around 2mm)
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- I have to place vias because of the pinout of USB C and CP2102. Some other people have done it with no problems
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#### CH340C
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- Ch340 Datasheet: p10 -> 100nF between GND and V3.
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- Ch340 Datasheet: p10 -> 100nF between GND and Vcc. Vcc to Vusb
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#### AMS1117
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- AMS1117 p4 -> 22uF tantalum capacitor on output
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- I will use a 22uF to reuse the same capacitor
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- I will reuse the output capacitor of AMS1117-5V to be the output capacitor of AMS1117-3.3V
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#### 5V autoselector
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- If USB is present and no external input voltage. The USB will power the ATMEGA
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- If USB is present and there is external input voltage. The external voltage will power the ATMEGA
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- If USB is not present and there is external input voltage. The external voltage will power the ATMEGA
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## KiCad Render
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<p align="center">
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<img src="https://github.com/Hanqaqa/Easyduino/blob/master/Atmega328p%20Arduino%20Uno/ProductionFiles/Photos/Easyduino%20Atmega%20Render%20Iso.jpg" width="60%">
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</p>
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