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Connecting Rotary encoder with 1024 ppr,line driver ouput 5V(A B Z) with TMS32028335 3.3V DSP processor

Joseph Peter
Intellectual 665 points
Other Parts Discussed in Thread: CONTROLSUITE

hi

i am using E50S8-1024-6-L-5 rotary encoder with 1024 ppr and have signals A B Z with line driver output of 5v connecting to a Texas Instruments DSP processor (TMS32028335 ).I  go thorugh the the code given in the: ti\controlSUITE\libs\device_support\f2833x\v132\DSP2833x_examples_ccsv4...

1)i can connect A B Z Signals to the qep module of processor right. with pins(5V A B Z Gnd)?

2) how can i convert 5v signals to 3.3 v before connecting to a dsp? should i initailise or configure any thing  else in tms32028335 dsp processor codings?

3)When i am using a floating point processor should i change any program of position speed calculations...in this program there are some lines with IQ MATH LIB...is that needed for a floating point processor..

eg:

if (newp>oldp)

Tmp1=-(_IQ(1)-newp+oldp)?etc

     Hope u can answer my queris..it would be grateful if you could help me regarding the same......thanking you in advance

Regards

Joseph

  • 0
    TI__Guru 57255 points

    Hi Joseph,

    1) & 2) 
    The eQEP module will do what you want, but you need to convert the 5V signals into 3.3V signals before attaching the encoder to the C2000 device.  Inside controlSUITE, the schematics for the TMDSHVMTRPFCKIT can provide you one starting point (which utilizes a voltage translator chip):
    \controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\~HVMotorCtrl+PFC-HWdevPkg\HVMotorCtrl+PFCKit-R1.1\

    A voltage divider + some diode circuit protection may also be okay if you work through it carefully.  The negative of this is that extra delay may be added and the signalling may not be as clean as the above..

    3) IQMath function calls have a bit of a 'trick' in them.  If floating-point FPU support is enabled in the compiler settings, IQMath calls will be redirected such that they use the floating point unit.  If fpu support is disabled, IQMath will be used.  This 'trick' allows the code to be more portable between fixed- and floating-point devices. You can find more about this at the link below and in other documentation:
    http://processors.wiki.ti.com/index.php/IQmath_Library_for_C28x


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Intellectual 665 points

    HI B rett

     thanks a lot

    1) can we use Sin Cos functionss as it is for 28334 dsp processor provided we define math.h?

    eg: sin (alpha-pi/3)

    else what we have to do?