Thursday, July 12, 2007

Quickies

From now on my preference will be operas, cinemas and theatres, since they are less crowded, less noisy, food is better and everything is cheaper than in the teenager-oriented beer parties.

The ATmega16 board I have worked with many weeks is almost coming together. We have the stepper nicely running, light intensity regulation works fine and the reflex sensor is on the right level (installed reflector on the rotating platform). Customer shall be happy again!

Saturday, July 7, 2007

Production

We will keep separate room for production. I spent three hours assembling all the equipment and tools required for optics assembly. If some were lost, it would have taken even more time.

We will complete the assembly instructions. The need was verified by redoing calibration again and again because of minor errors. A nice checklist would have saved a lot of time.

Thursday, July 5, 2007

Microstepping


Microstepping lets steppers work much faster and more reliably, not to mention smoother ride :P

The TCA3727 (looks like it will be obsolete shortly) has the following nice diagram explaining microstepping currents.

Stepping table is as follows:
#define I10 _BV(STEPPER_I10_PIN)
#define I11 _BV(STEPPER_I11_PIN)
#define PH1 _BV(STEPPER_PH1_PIN)
#define I20 _BV(STEPPER_I20_PIN)
#define I21 _BV(STEPPER_I21_PIN)
#define PH2 _BV(STEPPER_PH2_PIN)

static const u08
stepper_steps[] PROGMEM = {
I10 | I11 | 0 | PH2 | 0 | 0, // 0
0 | I11 | PH1 | PH2 | 0 | 0, // 1
I10 | 0 | PH1 | PH2 | 0 | 0, // 2
0 | 0 | PH1 | PH2 | 0 | 0, // 3
0 | 0 | PH1 | PH2 | I20 | 0, // 4
0 | 0 | PH1 | PH2 | 0 | I21, // 5
0 | 0 | PH1 | PH2 | I20 | I21, // 6
0 | 0 | PH1 | 0 | 0 | I21, // 7
0 | 0 | PH1 | 0 | I20 | 0, // 8
0 | 0 | PH1 | 0 | 0 | 0, // 9
I10 | 0 | PH1 | 0 | 0 | 0, // 10
0 | I11 | PH1 | 0 | 0 | 0, // 11
I10 | I11 | PH1 | 0 | 0 | 0, // 12
0 | I11 | 0 | 0 | 0 | 0, // 13
I10 | 0 | 0 | 0 | 0 | 0, // 14
0 | 0 | 0 | 0 | 0 | 0, // 15
0 | 0 | 0 | 0 | I20 | 0, // 16
0 | 0 | 0 | 0 | 0 | I21, // 17
0 | 0 | 0 | 0 | I20 | I21, // 18
0 | 0 | 0 | PH2 | 0 | I21, // 19
0 | 0 | 0 | PH2 | I20 | 0, // 20
0 | 0 | 0 | PH2 | 0 | 0, // 21
I10 | 0 | 0 | PH2 | 0 | 0, // 22
0 | I11 | 0 | PH2 | 0 | 0 // 23
};

#undef I10
#undef I11
#undef PH1
#undef I20
#undef I21
#undef PH2

When doing it step-by-step, some steps seem to be less "powerful" than others. It doesn't run _very_ smoothly on higher speeds. Perhaps some tweaking with step timings is neede in order to achieve really smooth operation.

Bugger lost it :)

Got this bugger to work. Turned out that the debugging output interfered with the timing of communications.

The mitutoyo cable was misconnected, thus I reconnected it and presto - all works fine!

Wednesday, July 4, 2007

Harvard Architecture Lesson

AVR has Harvard architecture. The program and data memory are totally separate entities. However, pointers to program memory have the same type as pointers to data memory.

This solved my yesterdays mysterious printouts. I was passing "const char*" to a function that was expecting "const prog_char *".