Hello together,
I need to steer a CPLD test mode via SPI in my project but the lowest SPI speed is just too fast for the CPLD.
So, instead of using SPI on pins 11-Data,13-Clock I used the shiftOut_lsbFirst function on a Teensy 3.2 on these pins.
Transferring a byte tooks 4ms which works fine (Signal Pin 13):
Used function:
Using the code on a Teensy 4.0 on the same pins doesn't work. I'm not getting any signal on the clock pin 13. Checking the definition of shiftOut_lsbFirst inside digital.c doesn't give me any hint why I'm not able to produce any clock signal. Can someone give me a hint how I can shift out 3 bytes in 12ms?
Snippet of .platformio.packages.framework-arduinoteensy.cores.teensy4.digital.c:
I need to steer a CPLD test mode via SPI in my project but the lowest SPI speed is just too fast for the CPLD.
So, instead of using SPI on pins 11-Data,13-Clock I used the shiftOut_lsbFirst function on a Teensy 3.2 on these pins.
Transferring a byte tooks 4ms which works fine (Signal Pin 13):
Used function:
Code:
//*--------------------------------------------------------------------------------------------------------
// send 3 bytes to the CPLD via shiftOut
//*--------------------------------------------------------------------------------------------------------
void SetCPLD_SO(uint32_t buf) {
uint8_t bytes[3];
bytes[0] = buf & 0xFF;
bytes[1] = (buf >> 8) & 0xFF;
bytes[2] = (buf >> 16) & 0xFF;
Serial.print("CPLD set: ");
for (int c = 0; c < 3; c++)
{
Serial.print("0x");
Serial.print(bytes[c], HEX);
Serial.write(' ');
}
Serial.print('\n');
#ifdef shiftOut
digitalWrite(slaveSelectPin,HIGH);
delayMicroseconds(250);
shiftOut_lsbFirst(shiftOut_Data,shiftOut_Clock,bytes[0]);
shiftOut_lsbFirst(shiftOut_Data,shiftOut_Clock,bytes[1]);
shiftOut_lsbFirst(shiftOut_Data,shiftOut_Clock,bytes[2]);
delayMicroseconds(250);
digitalWrite(slaveSelectPin,LOW);
delayMicroseconds(250);
digitalWrite(t_EnablePin,LOW);
delayMicroseconds(250);
digitalWrite(t_EnablePin,HIGH);
#endif
}Using the code on a Teensy 4.0 on the same pins doesn't work. I'm not getting any signal on the clock pin 13. Checking the definition of shiftOut_lsbFirst inside digital.c doesn't give me any hint why I'm not able to produce any clock signal. Can someone give me a hint how I can shift out 3 bytes in 12ms?
Snippet of .platformio.packages.framework-arduinoteensy.cores.teensy4.digital.c:
Code:
static const unsigned maxSpeed = 10000000ULL; //10 MHz
static const unsigned maxSpeedBeforeDelay = 392000000ULL; //max F_CPU_ACTUAL before doing delays (measured for 10MHz, -O2)
void shiftOut_lsbFirst(uint8_t dataPin, uint8_t clockPin, uint8_t value)
{
uint8_t mask;
if (F_CPU_ACTUAL > maxSpeedBeforeDelay) {
uint32_t cycles = (F_CPU_ACTUAL / 2 / maxSpeed);
uint32_t t = ARM_DWT_CYCCNT;
for (mask = 0x01; mask; mask <<= 1) {
digitalWrite(dataPin, value & mask);
do {;} while(ARM_DWT_CYCCNT - t < cycles);
t += cycles / 2;
digitalWrite(clockPin, HIGH);
do {;} while(ARM_DWT_CYCCNT - t < cycles);
t += cycles;
digitalWrite(clockPin, LOW);
do {;} while(ARM_DWT_CYCCNT - t < cycles);
t += cycles / 2;
}
}
else
for (mask=0x01; mask; mask <<= 1) {
digitalWrite(dataPin, value & mask);
digitalWrite(clockPin, HIGH);
digitalWrite(clockPin, LOW);
}
}