LMX2820: LMX2820 FPGA SPI

Da Feng

Part Number: LMX2820
Other Parts Discussed in Thread: LMX2572, , USB2ANY

I've implemented SPI for LMX2820 with Cyclone IV E. But it does not seem to be stable. I have followed timing for lmx2572. Occasionally, R0 has the same value, other time it does not. Also, R2 has 0x81F4 written, but always read as 0xB378 instead. Should I modify the signal level of I/O port of Cyclone IV E (EP4CE10)? Or should I modify other setting in Quartus? The registers written are copied from a STM32 projects, which works correctly. The register sets need to be written twice to have VCO correctly locked.

over 2 years ago

+1 Noel Fung over 2 years ago

TI__Guru** 109470 points

Hi Da Feng,

To debug, you should capture the SPI waveform to check if the timing, level and pattern is correct. In addition, if you are running SPI at high speed, try reduce the speed to improve signal integrity.

0 Da Feng over 2 years ago

Prodigy 20 points

I looked for voltage converters, from 3.3V TTL to 5V SPI. Is that necessary? The USB2ANY programmer works correctly, but my FPGA voltage does not. Could that be the cause?

0 Ajeet Pal over 2 years ago in reply to Da Feng

TI__Genius 12560 points

Hi Da Feng,

Is that the 5V SPI interfaced to LMX2820? LMX2820 can operate SPI interface with Vcc (3.3V). Hence the SPI interface level should be up to 3.3, which same as from USB2ANY.

Thanks!

Regards,
Ajeet Pal

0 Da Feng over 2 years ago

Prodigy 20 points

I'm looking for a STM32H7 now. It has both high baud-rate SPI interface and fast enough on-chip ADC. The XILINX devices seem to have XPS interface and Cyclone does not have. Since STM32 has dedicated GPIO pins for SPI, I think it not the problem of logic implementation.

0 Ajeet Pal over 2 years ago in reply to Da Feng

TI__Genius 12560 points

Hi,

I think for debug, please capture the SPI waveform and see the performance.

Thanks!

Regards,
Ajeet Pal

0 Da Feng over 2 years ago in reply to Ajeet Pal

Prodigy 20 points

I find adding guard time between transmission of data and setting I/O pin to 3.3 V LVTTL can write register content successfully.

Clock & timing

Clock & timing forum

LMX2820: LMX2820 FPGA SPI