Note how the code uses the SREG T-bit to flag the first vs. I have also tried with SPI. I do not what I am doing wrong, I receive only zeros. Below the function I use to send and receive the data. Data word length is 32 bit, the data is transfered MSB first, SPI mode is 0 (zero). ![]() When the conversion process is complete, the function loops back and converts the second nibble. I am trying to communicate with acceleration sensor via SPI bus. The function then converts the first nibble. Notice at the start of the code, that the constraint #0 value ( val) is temporarily saved in the r25 register. The following code converts a byte value into a hexadecimal string. For instance, I do not believe there is a 'SYN' line in the standard SPI bus. Instead, you may need to bit-bang this out totally in software. I am inclined to say you can not use the Arduino SPI library. In addition to these examples, have a look at the Arduino Inline Assembly Blink Program. The STPM10 timing diagram found on page 11 of its spec does not look like a standard SPI transaction. Each example includes explanatory comments covering the key portions of code. The goal here is to show complete and working demonstrations of how to include inline assembly into the typical arduino program. Most of the previous examples in this series were simple “snippets of code”, and as such gave a myopic view of inline assembly. Do not take these functions as archetypical examples of high-quality coding practice or brilliantly efficient inline code. ![]() The eighth bit disables the SPI interrupt, the seventh bit enables the SPI, the sixth bit chooses transmission with the most significant bit going first, the fifth bit puts the Arduino in Controller mode, the fourth bit sets the data clock idle when it is. In the control register each bit sets a different functionality. Specifically, these cover the conversion of a byte to a hexadecimal string, SPI Mode 0 hardware transfer, SPI Mode 0 Bit-banging, and the C library atoi function. Now we set the SPI Control register (SPCR) to the binary value 01010000. As the final tutorial in this series, we present four example inline assembly functions for the arduino.
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