Part Number: LAUNCHXL-F280025C
Other Parts Discussed in Thread: SYSCONFIG, TMDSFSIADAPEVM
Background
Running a 1-leader, 7-node FSI daisy-chain similar to the application note with similar 1-leader and 8-node.
I've worked through the example code and was able to get similar PWM jitter measurements as the application note.
I'm moving the lead and node code into new projects with SysConfig board.h/.c to perform the initializations.
My current configuration is also fairly crude wiring with Dupont-style jumper wires going board-to-board while I work on an comms isolation board, with that I'm running 25 MHz FSI clock (which also helps facilitate easier debugging of how the daisy-chain initializes and responds to node resets etc. with a logic analyzer)
Observations
The SysConfig sections for FSI do not include any checkboxes/dropdowns for setting the GPIOs to be qualification async.
The associated GPIOs selected in the FSI section don't auto-populate anything into the GPIO section (if you populate for example the LED section, the GPIO section auto-populates).
Upon building, the auto-generated board.h/board.c files do not set any qualification for the FSI GPIO pins.
With my new project that doesn't set any qualification on the FSI GPIOs, my PWM jitter has improved significantly, down to 16-20ns (was in the 70ns range)
Two questions
1. How critical is it to set the FSI GPIO pins to qual async if I would like to run the FSI clock up to 50 MHz? I'm not seeing CRC or other errors popping up running at 25 MHz now, though I haven't run it overnight.
2. Where is best to include the GPIO qualification setting function calls? I've included a code snippet of where I've tested the GPIO qualification. the Board_init() is the auto-generated function from SysConfig.
//
// Main
//
void main(void)
{
Device_init();
//
// Initialize PIE and clear PIE registers. Disables CPU interrupts.
//
Interrupt_initModule();
//
// Initialize the PIE vector table with pointers to the shell Interrupt
// Service Routines (ISR).
//
Interrupt_initVectorTable();
SysCtl_disablePeripheral(SYSCTL_PERIPH_CLK_TBCLKSYNC);
//GPIO_setQualificationMode(DEVICE_GPIO_PIN_FSI_RX0, GPIO_QUAL_ASYNC);
//GPIO_setQualificationMode(DEVICE_GPIO_PIN_FSI_RXCLK, GPIO_QUAL_ASYNC);
Board_init();
SysCtl_enablePeripheral(SYSCTL_PERIPH_CLK_TBCLKSYNC);
