So i kept getting an error code from the purepath device over SPI, the error when decoded read as follows "SPI error"
further reading show that the TI purepath is very picky about when to start the SCL, it's the slave device on the SPI bus so of course it should be picky.... right?
?
well contacting TI offered a solution, they have an interrupt system, great! so how do i use it? It's not described in the documentation, so I hook a scope up to the interrupt pin, sits there high and noisy , regardless of operation mode, a guess leads me to try a pull down resistor, ok it's toggling now, so i pull CS low and the interrupt sits low, hmmm.
By my understanding this pin was supposed to tell me when i could start the SCL but the line dies as soon as i try to start SPI coms.
Further reading = lots of people in the same boat.
TI suggest their own range of MCU's instead of a PIC, but that is hardly the issue, the SPI on the PIC is driving the gLCD without a bother.
As things stand:
The project is capable of transmitting audio across a Purepath network, so the devices work once paired and the audio codecs work.
The GUI and gLCD are complete, there was an issue with running the keypad from the +ve supply , but using a spare PIC o/p to enable the keypad solved this, basically applying +ve supply to PIC pin A4 shorted out the capacitors on the charge pump for the screen, so now the keypad is only enabled as it is being scanned for an input, leaving the rest of the time for the capacitors to charge to their required voltages for the gLCD.
So software is all that remains to be tidied, the non existent info on the interrupt opperation has me guessing in the dark, as the purepath device needs to finish any I2S, I2C and Wireless action before an SPI command can be read, I've assumed the device will interrupt the PIC, as a "Hello, I'm ready", but watching it on a DSO and setting my pic to trigger on the -ve edge of an interrupt did not resolve the problem. So this is still to do.
Time is up and the project was submitted, landed me a high grade for it so i'm pleased with the outcome. But it is still bugging me that i didnt get it 100% functional, to the point where i'm contemplating buying a Purepath Dev kit for nearly €300. I hate leaving things not finished, maybe TI know this and have baited me to boost sales? At the moment I'm in a dilemma, the project i built is the property of my Uni, as is the Dev kit i was using. So in order to complete this project for no increase in grade, do i spend on the Kit, and then recreate my PCB privately with no access to Uni PCB facilities, order some codecs, a screen more break out boards etc or do i just chalk it down to experience and move on?