On 2/28/18 10:33 AM, [email protected] wrote:
Hi Mark,
I am interested in doing the same thing (i.e. a
basic hall effect sensor connected to the
encoder channel on BB Blue).
Can you provide more details on how you got it
to work?
How did you change the control registers in the
eQEP hardware?
Could you provide a code sample that I could use?
Justin
On Sunday, June 25, 2017 at 2:12:34 PM UTC-6,
Mark Barton wrote:
On 6/25/17 3:20 PM, Przemek Klosowski wrote:
On Fri, Jun 23, 2017 at 10:05 AM, Clark
Sann <[email protected] <javascript:>> wrote:
Since you don’t care about direction,
for now, you might try hooking the
encoder to just the A channel.
If the decoder is in quadrature mode, this
probably won't work---it needs the B
channel signalling to disambiguate the
direction, so I think the counter will not
change. This is just my guess based on
general knowledge, so I may be
wrong---check it for yourself.
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Yep as you and Clark have surmised, neither
connecting the pulse to A and B would work
nor connecting just the A input. The counter
would sometimes decrement if A and B were
connected, and the counter would simply
toggle from 1 to -1 if only A was connected.
However the good news is I was able to get
it to work by changing one of the control
registers in the eQEP hardware to a simple
up count. The encoder pulse is connected to
the A input whereas B is not used. The pulse
count is now solid on both channels.
Mark
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Hi Justin,
I modified the roboticscape source that changed
the QDECCTL EQEP register. This changed
the encoder from expecting a quadrature input to a
simple up counter. Input A should be used
to sense the hall effect pulses. I can't remember,
but I do believe I had to ground input B
This will only work for the first three encoders
as the fourth is handled by the PRU.
I fully intended to submit my changes so hopefully
they would end up in mainline code,
however I am not familiar PRU what changes were
needed for the PRU. Of course I
moved on to other projects.
I hope this helps
Mark
Here are the sections of code I changed:
In roboticscape.c (just a comment change)
/*******************************************************************************
* int rc_set_encoder_mode(int ch, int mode)
*
* set encoder for quadrature pulses or single
pulse. Single pulse on input A
*******************************************************************************/
int rc_set_encoder_mode(int ch, int mode){
if(ch<1 || ch>4){
fprintf(stderr,"Encoder Channel must be
from 1 to 4\n");
return -1;
}
return write_eqep_mode(ch-1, mode);
}
In rc_nmap_pwmss.c
This is where the real change takes place
//set encoder to quadarature or single pulse mode.
int write_eqep_mode(int ch, int val){
if(init_eqep(ch)) return -1;
if(val == MODE_SINGLE_PULSE)
*(uint16_t*)(pwm_base[ch]+EQEP_OFFSET+QDECCTL) =
0x8000;
else
*(uint16_t*)(pwm_base[ch]+EQEP_OFFSET+QDECCTL) = 0x0;
return 0;
}
In rc_mmap_pwmss.h
//defs for setting encoder mode
enum{
MODE_SINGLE_PULSE,
MODE_QUADRATURE
};
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