DRV8301 2 Quadrature Encoder

Hi Mr. Schenk,

You have a few options available to you, but most take a little bit of effort.

1) Upgrade to the F28069ISO controlCARD - change out the F28035ISO controlCARD and instead put in a F28069ISO controlCARD.  The reason is that the F28069 MCU has 2 separate QEP modules which you can easily compare in software.  You could then edit (blue-wire & cut traces) the PCB board such that your new encoder ties into QEP2.  If it were me I would make use of J10 and U7 and try to patch into the nets 'CAP1'-'CAP3'.  This is the approach that I would recommend.

2) You could still use the F28035 and devise an implementation in which your software keeps up with the position.  The software would configure an interrupt to occur when the A&B signals change state.  The issue here is that you'll need to control the counting completely in software (and eat up cycles to do this).  However, the bigger problem  is that you'll  need to make sure that the transition can happen, the interrupt occurs and the interrupt finishes before a new transition arrives.  If another transition happens too quickly, your software encoder could miss a transition and the position value given by the software encoder will not be correct.

Hopefully this makes sense. 


Thank you,
Brett

Brett Larimore said:

Hi Mr. Schenk,

You have a few options available to you, but most take a little bit of effort.

1) Upgrade to the F28069ISO controlCARD - change out the F28035ISO controlCARD and instead put in a F28069ISO controlCARD.  The reason is that the F28069 MCU has 2 separate QEP modules which you can easily compare in software.  You could then edit (blue-wire & cut traces) the PCB board such that your new encoder ties into QEP2.  If it were me I would make use of J10 and U7 and try to patch into the nets 'CAP1'-'CAP3'.  This is the approach that I would recommend.

2) You could still use the F28035 and devise an implementation in which your software keeps up with the position.  The software would configure an interrupt to occur when the A&B signals change state.  The issue here is that you'll need to control the counting completely in software (and eat up cycles to do this).  However, the bigger problem  is that you'll  need to make sure that the transition can happen, the interrupt occurs and the interrupt finishes before a new transition arrives.  If another transition happens too quickly, your software encoder could miss a transition and the position value given by the software encoder will not be correct.

Hopefully this makes sense. 


Thank you,
Brett

Dear Brett,

I am sorry for the late question, but I saw this could be helpful to me.

You say it is possible to connect a second encoder to J10 (CAP1-CAP3), and these are wired to GPIO40-42. If I look in the datasheet of the F2806xM controlcards, GPIOs 40-42 don't mention eQEP as a terminal function, as opposed to GPIO 20,21,23, which are wired to the QEP module.

I am already using the first QEP (J4), but I would like to add a second one. Can I just connect it to J10, or do I need to wire the appropriate GPIOs (with eQEP terminal function, like 54-55-56) to some external pins or to J4, with a custom PCB?

Thanks in advance.

Hello,

You won't be able to connect up two encoders without editing the PCB board.

If you wish to edit the board, you'd probably want to blue-wire patch U7.5-7 to pins on the C2000 which have QEP functionality.


Thank you,
Brett