PROMPT - Project for Recording, Observing, and Measuring Parachute Tube

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• Louis Fleisher (RIT Student) correclty correctly ID'ed that there is not really a need for local logging, since if there is no 485 connection that very likely means that there is no power coming to the board either. However, it is a very small cost to add it now which gives us more flexibility down the road. It also opens up the possibility of independent operation in the future. 

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PROMPT is primarily intended to operate off of the regulated 5v provided from the backplane through the sensor board's connection. To allow for PROMPT to be utilized independently, the power system should be rated to allow for the direct connection of a 1S LiPo battery. This will include all the requisite battery protection circuits, such as reverse-polarity protection and over-current protection. Current consumption is expected to be <100mA, closer to 30-50mA. A jellybean priority mux circuit will be implemented to force a selection between the 5v and battery connections. The output of this mux will then go through a boost converter to regulate it to a clean 5 volts. 

Comments/Questions:

• Louis Fleisher (RIT Student) and Mary Dertinger (RIT Student) correctly ID'ed that there is no need to boost to 5 volts, since most devices are 3.3 volts. There is still more to look at in this section though...
• Battery power does not need to be raised to 5V to power RS485 chip because if the board is on battery power then it likely is not able to communicate with Backplane anyways. 
• Use a Linear Regulator (LDO) to lower battery voltage to 3.3V because it will create a low noise rail. 

Human Interface:

2 debug LEDs will show the state of PROMPT at a glance. A CP2102N is integrated on the board to act as a UART-USB bridge, providing both a debugging interface and a means of downloading data from the board if it is being operated independently of the backplane. 

Comments/Questions:

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• USB t0 UART thing
• Where are  LEDS seLecti0n

Component Selection:

0-60PSI pressure: ABP2LANT060PG2A3XX

• Used by Sparkfun
• i2C interface
• Not on JLCPCB

Comments/Questions:

• a 

Thermocouple Amplifier: MAX31855 

• Used by Adafruit
• 3-Wire SPI interface
• Cannot be used with grounded thermocouples
• JLCPCB: C52028

Comments/Questions:

• a Me no like. 

RS485 Transceiver: MAX487

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• Unknown, probably STM32

Comments/Questions:

• a Pr0bs fine

Memory: W25Q128JVSIQ

• Same as most other devices on the backplane
• JLCPCB: C97521

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• Widely used by Adafruit and similar
• Input range from 0.5 to 5.5v
• Output adjustable from 2.2 to 5.5v
• 3.7A max current
• Pass-through mode when VIN > VOUT
• JLCPCB: C919459

Comments/Questions:

• a Use with |eanear dr0p d0wn