Review Power Input/Power Output pin modes for 3.3V, 5V and VIN pins #65
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Alarm-Siren
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Arduino_101_Shield symbol Change 3.3V pin to Power Output; the circuitry needs 5V for voltage translation buffers U15, U14 and U11. Given this fact, the 5V rail must be powered, which means the on-board 3.3V regulator would conflict with an external source of 3.3V power. |
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Arduino_Due_Shield symbol Change 3.3V pin to Power Output; the circuitry needs 5V for at least the USB-to-RS232 adapter IC6. Given this fact, the 5V rail must be powered, which means the on-board 3.3V regulator would conflict with an external source of 3.3V power. |
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Arduino_Leonardo_Shield Change 3.3V pin to Power Output; the circuitry needs 5V for at least the U1 and U2 (the main microcontrollers). Given this fact, the 5V rail must be powered, which means the on-board 3.3V regulator would conflict with an external source of 3.3V power. |
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Arduino_M0_Shield The module does not use 5V internally for anything, therefore the module could be powered directly from the 3.3V pin. Leave all pins as Power Input. Arduino_M0_Pro_Shield Cannot find a schematic to check: on the assumption that it has similar requirements to the M0 leave all power pins as Power Input. |
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Arduino_Mega2560_Shield Change 3.3V pin to Power Output. The microcontroller, IC3, is powered on 5V. Therefore 5V must be powered, which means on-board 3.3V regulator would conflict with an external source of 3.3V power. |
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Arduino_Micro_Socket Change 3.3V pin to Power Output. The microcontroller, U1, is powered on 5V. Therefore 5V must be powered, which means on-board 3.3V regulator would conflict with an external source of 3.3V power. |
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Arduino_Mini_x_Socket_y (all variants) Leave all power pins as Power Input. There is no 3.3V rail, and the module can be powered using either 5V or VIN. |
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Arduino_MRK_Zero_Socket The module only uses the 3.3V rail internally, therefore it could be powered directly on the 3.3V pin. However if a Li-ion battery is connected to the module there is potential for conflict: Li-ion batteries, if improperly charged, can explode. Therefore out of an abundance of caution I will set the 3.3V pin to Power Output, even it though it could be used as Power Input safely in no battery is connected to J2. Arduino_MKR_WiFi_1010_Socket This module has two different 3.3V rails powered from the 5V rail, only one of which is exposed to the external connections. Therefore the 5V rail must be present, so the 3.3V pin is always a Power Output. |
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Arduino_MKR_WAN_1310_Socket The module only uses the 3.3V rail internally, therefore it could be powered directly on the 3.3V pin. However if a Li-ion battery is connected to the module there is potential for conflict: Li-ion batteries, if improperly charged, can explode. Therefore out of an abundance of caution I will set the 3.3V pin to Power Output, even it though it could be used as Power Input safely in no battery is connected to J7. |
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Arduino_MKR_WAN_1300_Socket The module only uses the 3.3V rail internally, therefore it could be powered directly on the 3.3V pin - and unusually for the MKR family, the battery connection actually goes directly into the 3.3V rail! However if a Li-ion battery is connected to the module there is potential for conflict: Li-ion batteries, if improperly charged, can explode. Therefore out of an abundance of caution I will set the 3.3V pin to Power Output, even it though it could be used as Power Input safely in no battery is connected to X1. |
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Arduino_MKR_Vidor_4000_Socket This module has internal 2.5V and 1.2V rails which can only be powered from 5V or VIN (see part U4), therefore 3.3V must necessarily always be a Power Output. |
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Arduino_MKR_NB_1500_Socket This module has an internal 1.8V rail, though I cannot figure out where it is powered from. It also has the same battery arrangement as e.g. the Arduino_MKR_GSM_1400_Socket See Arduino_MKR_FOX_1200_Socket See Arduino_MKR_1000_WiFi_Socket See |
Reviewed up to the end of the MKR series.
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Arduino_Nano_Every Change 3.3V pin to Power Output. The microcontroller U1 is powered on 5V, Therefore 5V must be powered, which means on-board 3.3V regulator would conflict with an external source of 3.3V power. Arduino_Nano_33_IoT 5V pins is disconnected by default, so set pin type to Arduino_Nano_33_BLE 5V pins is disconnected by default, so set pin type to Arduino_Nano_33_BLE_Sense Datasheet and CAD data available on the Arduino website is incorrect; it is exactly the same as the Nano 33 BLE - which is impossible as the Sense has some extra components. Documentation does specify that 5V pin is disconnected by default, so set pin type to |
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Arduino_Nano_RP2040_Connect 5V pins is disconnected by default, so set pin type to Arduino_Nano Change 3.3V pin to Arudino_Pro_Mini This module can accept regulated voltage (3.3V or 5V, depending on model) on the Vcc pin, or unregulated voltage up to 12V on RAW. Therefore all power pins should remain Arduino_Uno_R3 Change 3.3V pin to Power Output. The microcontroller, U3, is powered on 5V. Therefore 5V must be powered, which means on-board 3.3V regulator would conflict with an external source of 3.3V power. Arduino_Uno_R3_SMD See |
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Arduino_Uno_WiFi_R2 See Arduino_Zero The module does not use 5V internally for anything, therefore the module could be powered directly from the 3.3V pin. Leave all pins as Power Input. Pro_Mini_Clone See |
Review the power input/output pins, to ensure that they have the correct Pin Type assigned.
In particular, some 3.3V-based modules actually do have some 5V-powered components. On these boards, it is important that 3.3V is marked as an 'output', as it would be inappropriate to feed 3.3V into the module through this pin - as this will conflict with the module's on-board 5V-to-3.3V regulator.
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