MySensorsNode Rev. 1.1

Features:

• Any Arduino Pro Mini with A6 and A7 pins available should fit this board (A6 and A7 is required to comply with MYSX specifications.
• Although the board can take both NRF24 and RFM69 at the same time mounted, they share pin for SPI chip select, so they cannot be used simultaneously (unless you patch the board to re-route one of the chip selects to a different Arduino pin and make the necessary SW modifications)
• Support the MySensors Expansion port (MYSX) in all versions up to 1.5. MYSX specifications is available here. Depending on what battery sockets are mounted on the board, the MYSX connector may have to be “raised” so a daughterboard can fit in some of the layouts of the board.
• Flexible options for battery measurement:
  • Voltage divider is implemented using a potentiometer (1M@RV1) which makes it possible to tune the sample voltage to optimize measurement range.
  • JP4 can be shorted to connect battery net directly to potentiometer (which in turn is connected to Arduino pin A0). A footprint for an optional decoupling capacitor is available at C8 to smooth the sample value. It is not recommended to use C8 if low-power sampling option is used.
  • With JP4 open, battery samples are taken by momentarily driving MYSX_D9_A3 low (Arduino pin A1). When sample is taken, MYSX_D9_A3 is set high again, which prevents continuous drain of battery through RV1. This assumes JP10 is shorted. If a daughterboard is connected that uses MYSX_D9_A3, analog samples taken on that pin might be affected by the 0.1uF capacitor (C9) when JP10 is shorted.
• Depending of power source used, two regulator options are available.
  • For “high” voltage sources a LDO provides the regulated 3.3V voltage. Maximum accepted voltage is 12V. This is enabled by shorting JP2 pos 2-3.
  • For “low” voltage sources a step-up voltage regulator provides the 3.3V voltage. Maximum accepted voltage is 4.2V. This is enabled by shorting JP2 pos 1-2. The step-up voltage regulator also implements a pass-through option in which the regulator is turned off and the input voltage is fed right through it. The pass-through is enabled by driving MYSX_D10_A4 low (Arduino pin A2) and shorting JP6. Be aware that this also goes through the MYSX connector, so it is not recommended to use this feature if a daughterboard is connected that uses MYSX_D10_A4. There are two footprints available for this regulator alternative; SC-70 (TI TPS61221) and SOT-23 (TI TPS61097A). Both has to be the 3.3V fixed version since there is no footprints for adjustment-resistors. Also note that these two regulators are mutually exclusive. Do NOT mount them both at the same time.
• All different power source options can be simultaneously mounted (not that it has to be). But on some layouts, the BT4 and BT5 (CR123 and coin cell) connectors one of the BT4 connector legs needs to be filed down if a coin cell battery is to be fitted. But the layout will ensure no shorts are risked. On the 5x5cm board, BT4 and BT5 are omitted due to size constraints.
  The following possibilities exist:
  • DC socket (BOM will use 2.5MM part with center pin being positive and shield ground.
  • Battery wires (or virtually any power source) can be connected to a 2.54mm pitch screw terminal (or soldered directly to the board).
  • A JST (S2B-PH-K-S) connector for LiPo cells (like this or this one).
  • A CR123 socket (not available on 5x5 cm board).
  • A 24.5mm coincell holder capable of accepting up to CR2477 sizes (not available on 5x5 cm board).
  • Vraw supply from a MYSX daughterboard.
• The 3.3V pin of the MYSX connector can be programmatically switched off.
  • To switch off the 3.3V supply pin drive Arduino pin D4 low. Leave it floating to have the 3.3V pin enabled.
• ATSHA204A HW signing is available (uses Arduino pin A3).
• 3 (switchable) 3.3V/GND rail pairs is available to allow discreet mounting of wired sensors (in excess to the pins available on the MYSX connector).
• An onboard SI7021 sensors is connected to the I2C bus to provide rudimentary sensor possibilities on the motherboard itself.
• An onboard AVR ISP programming socket provides the possibility to program a custom bootloader to the Arduino (useful for OTA).
• An external flash is connected to the SPI bus to permit OTA using the Dualoptiboot bootloader.

MySensorsNode Rev. 1.0

Features:

• Switchable battery level measurement (JP1 selects mode, sampling pin on A0, sample enable on A1)
• By-passable 3.3V step-up regulator (active high on D5)
• Possibility to disable sensor power rail (active high on D4)
• Optional additional 5V step-up regulator for sensors
• 2.5mm DC jack power supply footprint
• 2mm pitch JST connector for LiPo batteries
• Both RF24 and RF69 footprints and possibility for interrupt connectivity (CSn on D10, RF24 CE on D9, INT on D2 through JP5:3-2)
• External SPI flash (CSn on D7)
• AVR ISP programming header
• ATSHA204A authenticatior footprint (A3)
• On-board I2C pullups
• On-board sensor ports (Px:1 5V, Px:2 3.3V, Px:3 GND):
  • 1 PWM enabled sensor port (P4:4 to D6)
  • 2 HW interrupt sensor ports (1 optionally taken by radio) (P3/10:4 to D3/2)
  • 2 generic I/O sensor ports that also provide HW UART (P1/2:4 to D1/0)
  • 1 SPI header (P9:4 to MISO, P9:5 to MOSI, P9:6 to SCK, P9:7 to D7 (CSn))
  • 2 Analog sensor ports (P5/6:4 to A7/6)
  • 2 I2C sensor ports (P7/8:4 to A4, P7/8:5 to A5)

Known issues:

• The layout of CON1 is incorrect with respect to normal battery
  connectors so battery polarity will be reversed. Do NOT connect
  a battery with JST connector to this board (Rev 1.0).
• 3.3V regulator has an unterminated EN-signal. That means it could
  start up in "off" state which mean that if battery level is too high
  (>4.1V) SPI flash could fry. If battery level is too low (<1.8V),
  MCU might not start in order to enable the regulator.
  A workaround if this situation is undesirable is to solder a 1M Ohm
  resistor between REG_BYPASS and +BATT signals.
• Pull-ups are missing on SPC CS signals which may lead to undetermined
  behaviour on some SPI devices.
• If the 5V regulator (U2) is enabled through Q2, the large inrush current may cause the
  Arduino to reset due to momentary voltage drop of +3.3V rail. This can be resolved by
  bypassing the +3.3V rail with a large (~470uF) capacitor.