I had high hopes for this board, but the issues I see are a bit over my knowledge. Maybe someone can help.
I am trying to connect over I2C the board with two Nanos and after a few hours I realized that the serial interface offers SCL/SDA pins that are different than the one mapped to the clock (DS1307). According to the schematics DS1307 connects to SCL/SDA on pins PD0/PD1 (43/44) while serial interface calls SCL/SDA pins PC2/PC3 (55/56).
What is this ? I thought the name convention is unique. Is there a way to remap these pins ?
If this problem can not be solved, this board is pretty useless. Too bad, because it had everything on.
cheers,
MaLi
PS. A small I2C scanner sees only 0x68 (DS1307) which tells me that the wire library uses 43/44.
The hardware I2C controller inside the ATmega2560 chip is at PD0/PD1 (43,44).
The Arduino Wire library uses that.
The PC2/PC3 (55/56) are normal pins, without special function. When those have I2C, a software-i2c library is used. I think that is how the I2C display is used. They call it the "LCD SERIAL INTERFACE", that is confusing. It should be called "LCD I2C interface".
I spent some more time last evening and I ended up taking the SCL/SDA from the pins 5 and 6 of DS1307. Not very elegant and a significant problem with this board. What were they thinking when did not provide I2C access ??
A pity though. The board was running a webserver and was performing very well.
Peter, that is correct. J22 was suppose to be I2C, but a continuity test shows that those pins are not reaching out to SCL/SDA. I will try to trace the circuit, but is very difficult.
Peter, I learned something new. The SCL/SDA are indeed connected to J22, but through two transistors. Without powering the board there is no signal at J22 hence the failed continuity check. All is good so far. Thanks for your help.