Electrical – what does the “UL” means when specifying the clock speed for AVR MCUs

microcontroller

So I am using the ATTiny10 for the first time, and I noticed that even after setting the clock pre-scaler register correctly (0x00 in my case) I had to define a value called F_CPU for the _delay() function to work correctly. but when going over the code example I have there was #define F_CPU 8000000UL. What does the UL mean?

Also if someone can recommend a good book to start with microcontrollers that would be appreciated, too many registers and setup conditions it's overwhelming!.

Best Answer

The "UL" means unsigned long. The C/C++ language defines this and other type specifiers for integer literals. See https://en.cppreference.com/w/cpp/language/integer_literal

Related Solutions

Electronic – Cycle counting with modern CPUs (e.g. ARM)

I vote for DMA. It's really flexible in Cortex-M3 and up - and you can do all kind of crazy things like automatically getting data from one place and outputing into another with specified rate or at some events without spending ANY CPU cycles. DMA is much more reliable.

But it might be quite hard to understand in details.

Another option is soft-cores on FPGA with hardware implementation of these tight things.

Electronic – ADC registers setup using spi communication

While this datasheet is making my eyes bleed with the complexity of doing a simple conversion/read, you need to make some simple changes.

I'm not sure why people are making this harder than it really is. You pull the chip select line low, and the target IC should simply read whatever you give it until you pull it high again. Just because your method takes an 8-bit value doesn't mean you can't call it twice to pass a 16-bit value to your IC. There is no need to bit-bang anything. That is nonsense.

Call your SPI method to tell the ADC you're looking to write to the configuration register:

spi(0x10);

As I understand from the datasheet, you can immediately write your 16-bit value to the configuration register after that, so you'd do:

spi(0x07);
spi(0x10);

I forget which way that'll end up being assembled on the target IC side, so you could simply reverse them if things don't work right. There's no need to bit shift any values at all. Worst case scenario is you have to pull the CS line back high before pulling it low again to actually send the data to write to the configuration register.

Otherwise, this is super simple. Remember, if the target SPI device expects more than one byte, i.e. a 16-bit value, chances are good that sending the bytes in the order they'd otherwise appear normally (so if you want to send 0x1234, you'd have 0x12 and 0x34) will work fine and you won't need to shift anything.

Best Answer

Related Solutions

Electronic – Cycle counting with modern CPUs (e.g. ARM)

Electronic – ADC registers setup using spi communication

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