NIOS II/f altera_avalon_i2c, possible BUG in HAL

Altera_Forum · ‎10-19-2017

Hi,

I need a I2C master for my NIOS II/f. I thought using the I2C master which is shipped by Altera in Quartus Prime 17.0 should serve my needs.

However I'm a bit worried about the software quality of the HAL and drivers.

While testing I recognized that switching speed of the bus is not possible. The clock setting is fixed for 100kHz, setting other values results in wrong behaviour.

altera_avalon_i2c.c:302


ALT_AVALON_I2C_STATUS_CODE alt_avalon_i2c_master_config_speed_set(
   ...
   /* adjust h/l by predetermined amount */
   scl_hcnt = scl_lcnt + ALT_AVALON_I2C_DIFF_LCNT_HCNT;  // scl_lcnt+60, should be scl_lcnt+15 for 400kHz
   scl_lcnt = scl_lcnt - ALT_AVALON_I2C_DIFF_LCNT_HCNT;
   ...

Therefore ALT_AVALON_I2C_DIFF_LCNT_HCNT should be adapted to the speed setting.

Did I miss something? What is your experience with the NIOS II software drivers?

In addition, I could not find any proper documentation with examples. Do I really have to browse the header files to get infos about the API?

Cheers, Marc

Mosari · ‎06-15-2023

Thank You report this.

I could SCL drive 400k.

but Is it collect which using I2C Master API ?

I wrote cfg speed set secont argument "400000".

But I couldn't drive 400k.

So Google it and got this report.

Why Intel doen't fix it.

Anyway. Thank you.

jmcguire3 · ‎09-01-2023

Yes, this appears to be a bug in the HAL ... still ... after at least six years. I'm running an I2C bus on an Agilex part, and we added a peripheral that could run at 400kHz; we had previously been running the I2C bus at 200kHz without issue, though the generated clock looked like crap - duty cycle was nowhere near 50%.

In the file drivers/src/intel_avalon_i2c.h we changed:

//#define ALT_AVALON_I2C_DIFF_LCNT_HCNT 60
#define ALT_AVALON_I2C_DIFF_LCNT_HCNT 30

System runs fine at 100kHz, 200kHz and 400kHz now.

Edit:

Had better results dropping the ALT_AVALON_I2C_DIFF_LCNT_HCNT value to 10. Low-half of the SCL clock is right around 1us; high-half is nominally 1.4us.

Scope traces are attached. One shows the system not-running with the way-too-skinny SCL clock - ALT_AVALON_I2C_DIFF_LCNT_HCNT set to 50. The other (which works) has the parameter set to 10.

Mosari · ‎09-03-2023

Hi jmcguire3

Thank you for reply and post scope pic.

After that. I always use modify altera_avalon_i2c.h.

User need define ALT_AVALON_I2C_DIFF_LCNT_HCNT by speed for now.

I try 50kHz. So I set DIFF_LCNT_HCNT "120"

and using ALT_AVALON_I2C_SS_MAX_HZ = "50000".

Work is OK.

User need set thats manually.

reported.