128 lines
2.6 KiB
Markdown
128 lines
2.6 KiB
Markdown
A Raspberry Pi-compatible PCB that extends the GPIO header with protected I/O, relays, and various features for versatile use in prototyping and project development.
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**Notes:**
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# RPI Specs (Zero, 3+)
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- Available (old) Pi: Raspberry Pi 2 Model B v1.1
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- GPIO
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- Low: 0.9V
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- High: 1.6V
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- Input current: 5uA
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- Input capacitance: 5pF
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- Output Current +-17mA
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- Pullup / Pulldown 50-65k
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- EEPROM GPIO0 GPIO1, leave unused
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# Feature Ideas
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- [x] Temperature control
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- fan
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- auto turn on
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- temp sensor
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- ~~turn on via gpio~~
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## Supply
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- Input protection
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- [x] TVS
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- [x] reverse polarity (polyfuse will trigger)
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- [x] Fuse (5A polyfuse)
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- [x] buffer
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- [x] Pass through power supply
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- [x] 3.3V, 5V, 12V, 24V Regulator
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- [x] power by barrel connector (24V 5A)
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- ~~power by usb~~ [not allowed]
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- ~~Switch between power by USB or power supply?~~
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- ~~power by battery~~ [dropped]
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- liion cell connector
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- BMS / charge controller
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- measure battery voltage
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- USB charging port
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## IO
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- Input
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- GPIO
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- [x] wide voltage range (-1.7 to 120V)
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- [x] TVS
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- [x] reverse polarity (-1.73V max)
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- [x] Low pass filter
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- [x] Optocoupler input
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- [x] ADC
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- external IC
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- ~~multiplexer?~~
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- protection
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- scale input voltage
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- fixed inputs: 24V 12V 5V 3.3V
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- 20mA input
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- ~~trim potentiometer?~~
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- Output
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- [x] Relay
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- [x] Mosfet
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- [x] Optocoupler output
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- [ ] GPIO with over current protection
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- [ ] GPIO level shift (24V output)
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- [x] PWM pins
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- [x] shift register
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- [ ] DAC
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- [x] LEDS indicate I/O state
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- [ ] Testpoints
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- [x] ESD protection (tvs diodes uart, i2c...)
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## Bus
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- [x] UART/RS485
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- [ ] RS232 Connector
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- [x] I2C Pullup
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- [x] SPI
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- [ ] CAN
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- ~~Serial to usb (if Arduino)~~
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- ~~OWB default GPIO4~~
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## UI
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- Input [dropped]
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- Buttons
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- DIP switches?
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- Temperature sensor
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- Encoder
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- Potentiometer
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- Output
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- [ ] Display [RPI display pending]
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- [x] Buzzer
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- [x] LEDS
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## Mechanical
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- [x] Barrel plug (24V 3A supply)
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- ~~Screw terminals~~
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- [x] spring loaded?
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- ~~pass through all pins?~~
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## Housing
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- RPI ports
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- banana sockets for power out
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- screw terminal exposed
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- buttons, leds: need to open up?
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- BNC? []
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## Other
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- Extension board with multiplexer
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- Breadboard compatible?
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- SD Card
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- ~~Onboard MCU for standalone use?~~
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- ~~separate bought MCU via i2c for additional GPIO, DAC, ADC in one~~
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## Questions
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- what analog input ranges (Voltage, Count)
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- RS232 RS485 SPI, IIC actually necessary? examples
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- CAN to second SPI?
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- 8x shift register outputs, 0.5A open drain or 7mA tristate
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- 2x PWM 30A enough?
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- max used PWM freq? (drop opto if >80khz) |