Hello,
I have a microcontroller based shaft encoder device with its firmware already written. I have its python equivalent on serial protocol to read and write to the device:
##************************************************************
WRITE_KNOB = 121
READ_KNOB = 41
se = serial.Serial(port='/dev/ttyACM0', baudrate=38400, timeout = 0.3, parity=serial.PARITY_EVEN, stopbits=1)
def read_knob(kn):
se.write(chr(READ_KNOB))
time.sleep(0.01)
se.write(chr(kn)) # Knob kn=0, 1, 2, 3 to be read
time.sleep(0.01)
res = se.read(1)
if res != 'D':
print 'READ_KNOB error ', res
return
res = se.read(2)
data = "" | (ord(res[1]) << 8) # HIGH byte is comming First, Next -> LOW Byte
return data
def write_knob(kn,data):
if (data > 65535):
data = "">
dlo = data & 0xff
dhi = (data >> 8) & 0xff
se.write(chr(WRITE_KNOB))
time.sleep(0.01)
se.write(chr(kn))
time.sleep(0.01)
se.write(chr(dlo))
time.sleep(0.01)
se.write(chr(dhi))
time.sleep(0.01)
res = se.read(1)
print res
if res != 'D':
print 'WRITE_KNOB error ', res
return
return data
##*******************************************************
My equivalent .proto file for read is as follows and it is working fine:
get_analog_ch0 {
out ')'; # for chr(41)
wait 50;
out '\x00'; # for chr(0)
wait 50;
in "D%#02r";
#ExtraInput = Ignore;
ReadTimeout = 30;
@mismatch {
out ')';
wait 50;
out '\x00';
wait 50;
in "C%r";
}
}
But I am unable to write the data to it. The routine that I am using is:
set_analog_ch0 {
out 'y'; # for chr(121)
wait 50;
out '\x00'; # for chr(0)
wait 50;
out "%2c";
#ExtraInput = Ignore;
#ReadTimeout = 30;
}
The .db file is as follows:
record(ai, knob:get:ch_0) {
field(DESC, "Knob 0 output")
field(DTYP, "stream")
field(INP, "@encoder.proto get_analog_ch0() $(PORT)")
field(SCAN, ".05 second")
}
record(waveform, knob:set:ch_0) {
field(DESC, "Knob 0 output")
field(DTYP, "stream")
field(INP, "@encoder.proto set_analog_ch0() $(PORT)")
field (FTVL, "CHAR")
field (NELM, "2")
}
I am not sure whether waveform or which type of record will suffice here. While using waveform record, I am unable to write the 2 byte values to the record like the way it is being done in python serial interface code.
ps: I am an EPICS newbie. So, please bear with my limited experience.
--
Ashish Sharma
Engineer 'C'
Inter-University Accelerator Centre,
Aruna Asaf Ali Marg, New Delhi - 110067
Mob. : +91-9643031284, +91-7982808263
Off. : 011-24126024 (Ext : 124)
