Hello,
I have a PCB with 3 standalone ATMEGA2560 micro controllers. I am currently using a serial communication architecture between them. Each controller has its on SPI header for programming. I want to change to SPI communication with one defined as master and the other two as slaves. Will there be any problems with programming the two slaves if with their SS pin is tied to both the programming header and master output pin? In other words, a conflict caused by the programmer trying to pull the slave pin low while the master is trying pull it high at the same time.
Will there be any problems with programming the two slaves if with their SS pin is tied to both the programming header and master output pin?
No, I would not expect problems because of that.
In other words, a conflict caused by the programmer trying to pull the slave pin low while the master is trying pull it high at the same time.
The master (as well as the other slave) should be without power if you program the slave. If you cannot ensure that insert a resistor between the masters output pin and the slaves SS pin (p.e. 1kΩ).
Problem with SD card over SPI. Works for UNO but not Nano_33_IOT.
The Nano_33_IOT is 3x faster than the UNO and uses 3.3V levels. The SD card is part of a touch screen that uses both 3.3 and 5V. I don't have a data sheet that explains what levels are expected.
I don't have signal translators because I looked at the circuitry on this particular touch screen.
All the data and control signals go through 245 transceivers that have 3.3 supply voltage but have 5V tolerant inputs.
The SD device is powered by 3.3V. I think the 5V is for powering the LCD screen itself.
I don't have a scope here so I'm not 100% sure. The fact that it does recognize it as a SDHC card suggests it's not that problem. I suspect timing, but SPI should be pretty standard.
Here's the output from CardInfo:
Initializing SD card...Wiring is correct and a card is present.
Card type: SDHC
Could not find FAT16/FAT32 partition.
Make sure you've formatted the card