Reading Chapter 19 (SSP ...) of the User Manual, my understanding of the usage is that I should configure to use SSP0 (say) as SPI, and then use code similar to this:
void SSP_SPI_SR(uint16_t* sendBuffer, uint16_t* recvBuffer, uint8_t length) { uint8 len1 = length, len2 = length; // Ensure SSP receive FIFO is empty (by reading data out of it if necessary) while(SSP0SR & RNE) SSP0DR; IOCLR0 = 0x00100000; // SSEL active (down) while(len1 || len2) { if (len1 && (SSP0SR & TNF)) // Data to send and transmit FIFO isn’t full? { SSPODR = *sendBuffer++; len1--; // // add a wait loop here if need to prevent buffer underrun at slave } if (len2 && (SSP0SR & RNE)) // Data to receive and receive FIFO has data available { *recvBuffer++ = SSP0DR; len2--; } } } IOSET0 = 0x00100000; // SSEL inactive (up) } // Usage : uint16_t pollSequence[9] = {0xEBEB, 0xEBEB, 0xEBEB, 0xEBEB, 0xEBEB, 0xEBEB, 0xEBEB, 0xEBEB, 0xFFFF}; uint16_t pollReplies[9] = {0}; SSP_SPI_SR(pollSequence, pollReplies, 9);
Is that right?
If so I'm puzzled! Using CPOL=1, CPHA=0. Section 19.5.2.4 explicitly says:
However, in the case of continuous back-to-back transmissions, the SSEL signal must bepulsed HIGH between each data word transfer. This is because the slave select pinfreezes the data in its serial peripheral register and does not allow it to be altered if theCPHA bit is logic zero. Therefore the master device must raise the SSEL pin of the slavedevice between each data transfer to enable the serial peripheral data write. Oncompletion of the continuous transfer, the SSEL pin is returned to its idle state one SCKperiod after the last bit has been captured.
But given that the FIFO is being used for data transmission, I don't understand how I am supposed to toggle *SSEL between transfers.
Help greatly appreciated.
Thanks, David
If this is in the wrong forum, please could mods move it to the correct location.Anyone know the answer BTW?
Hello, which document are you referring to? I cannot find the reference in any LPC2388 documentation I searched for.
That being said, it does appear that your question is regarding specific behavior of an NXP device. You are more likely to get an appropriate answer on NXPs own forums than here:
https://community.nxp.com/t5/LPC-Microcontrollers/bd-p/lpc
I am referring to document UM10211 which is the official User Manual for the LPC2388:
LPC23XX User manual
Thanks for the pointer to the NXP forums I have posted there.
D.