atmegaatmega328pavrmicrocontrollerspi
I'm willing to use the Atmega328 microcontroller to control the AD9833 waveform generator through the SPI interface of the microcontroller; the only problem is that the AD9833 reads 16-bit data while the microcontroller's SPI is 8-bit based.
I have been told that the most intuitive solution to this (sending two consecutive bytes) doesn't work, ¿is this true?
If it is, ¿is there anyway I could interface the two devices in order to implement the communication?
Bit banging is creating the whole series of pulses in software, instead of relying on a piece of hardware inside the microcontroller.
Many microcontrollers have a hardware SPI, and then all you have to do is write a byte to the output register, and the SPI controller will shift the data out, and at the same time receive data from the slave. You can get an interrupt when the transfer is complete, and then read the received data.
But some microcontrollers don't have the SPI hardware on board and then you have to simulate it by doing everything manually. SPI has a number of different modes, I'll use this pulse diagram as an example:
So while a dedicated SPI controller takes care of all the pulses, data shifting and timing, when bit-banging you have to take every action yourself:
Make Slave Select low
Short delay
Do 8 times
Make the SCK (Serial Clock) pin low
Make the MOSI (Master-Out-Slave-In) pin high or low depending on bit 7 of the data
Add brief delay
Make the SCK output high
Read MISO (Master-In-Slave-Out) pin
Shift received data left, and shift the bit just read in as bit 0
Add brief delay
Shift the data byte 1 bit left
Make Slave Select high again
Bit-banging SPI is relatively simple, the code for bit-banging I2C for instance will be more complex, and you'll need a timer somehow if you want to bit-bang the UART protocol.
SPI is a full-duplex protocol. In order to receive data, you have to send data at the same time, even though the Flash chip might do nothing with the data that you send.
So, for example, you want to read the JEDEC ID. You lower the /CS signal and send the "read JEDEC ID" command. That command instructs the Flash chip to "send your JEDEC ID and do nothing with any other data that you receive". You keep sending data (which is all zeroes and will be ignored anyway), and as you do so it sends you back its JEDEC ID - you get back one byte of JEDEC ID for each zero byte that you send. When you raise /CS at the end of the transaction, that resets the Flash chip's controller.
Best Answer
The datasheet answers this in the section about interfacing to an 68HC11 series microcontroller on page 20 of the datasheet:
You just need to keep fsync low, and send another 8 bit data stream to the device.