it shows pin Arduino pins 52 & 51 (Atmega pins 20 & 21) as SDA and SCL.Digital pins 21 & 20 (Atmega pins 43 & 44) are also labeled SCL and SDA.
No the I2C lines are on pins 20 & 21, where as the clock and data for the SPI interface are on pins 51 & 52, it might not be clear but it is not wrong.
It's not a JPEG image, it's a PNG. You need to save it out as the proper format.
Unless there are two SDA and two SCL, one of them must be wrong. (Most likely the latter).
• INT3/TXD1 - Port D, Bit 3INT3, External Interrupt source 3: The PD3 pin can serve as an external interrupt source to the MCU.TXD1, Transmit Data (Data output pin for the USART1). When the USART1 Transmitter is enabled, this pin is configured as an output regardless of the value of DDD3.• INT2/RXD1 - Port D, Bit 2INT2, External Interrupt source 2. The PD2 pin can serve as an External Interrupt source to the MCU.RXD1, Receive Data (Data input pin for the USART1). When the USART1 receiver is enabled this pin is configured as an input regardless of the value of DDD2. When the USART forces this pin to be an input, the pull-up can still be controlled by the PORTD2 bit.
All Arduino RXs and TXs are wrong.
...pin numbers on top and bottom side of the png image are messy....
Why can't you see this?
QuoteWhy can't you see this?Because the terms SCL and SDA are not used exclusively to describe I2C pins.They reffers to Serial Clock Line and Serial DAta, there is nothing in the convention that says these have to be I2C.
You miss the point. We know that we can go elsewhere for the proper pinouts, but the point we make is that the official Arduino documentation is wrong and could mislead those take it for gospel. It should be corrected.