The model Zero-W is adds on-board Wi-Fi, Bluetooth and the Pi camera connector to the existing model Zero board.The model B v3 features a quad-core Arm A8 processor (64-bits) with the same RAM and GPIO as the model 2, however it also features on-board Wi-Fi and Bluetooth.40-pin GPIO connector and very little else. The model Zero is a souped-up (1GHz) cut down Pi A+.The model B v2 features a quad-core Arm A7 processor with 1GB of RAM.The model A+ and B+ Raspberry Pi’s represents 2 years of research, development and testing and now features a single 40-pin GPIO connector with 28 usable GPIO pins and 4 USB sockets.The model A which is essentially the same as the model B v1.1 but without the USB hub and ethernet connector.The model B, Revision 1.1 Raspberry Pi has an additional 4 GPIO lines on a separate connector which you have to solder onto the board.The original model B with the 26-pin GPIO connector.Over the years there have been some updates: Additionally there is a 2-wire I2C interface and a 4-wire SPI interface (with a 2nd select line, making it 5 pins in total) and the serial UART with a further 2 pins. Two of these pins (on 40-pin Pi’s, just one on 26-pin Pi’s) can be designated for hardware PWM output too. There are 8 general purpose digital I/O pins – these can be programmed as either digital outputs or inputs. The original Raspberry Pi Model A and B version B1 was a $35 single board computer with a 26-pin General Purpose Input/Output (GPIO) connector and this carries a set of signals and buses.

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