I don't know if you've already solved this problem, but here's some code to read input from a Cedrus response pad (in our case, the RB-830 model). You need to install the pySerial package first (http://pyserial.sourceforge.net). Mason Smith Lab Manager Language and Cognitive Architectures Lab University of Michigan Lab phone: 734-764-6827 Cell: 734-272-4883 |
import serial
import pygame
pygame.init()
BBOXMAPPING = {0:4,6:3,5:2,2:1,1:5,4:6,3:7,7:8}
def byteToKey(byte):
return (BBOXMAPPING[ord(byte)/32],(ord(byte)/16)%2)
#Open a serial port at COM2 with baud rate 115200
#(or in this case, a USB port masquerading as a serial port)
ser=serial.Serial(2,115200)
#Record when we reset the bbox's timer
clock=pygame.time.Clock()
#Send a message to the bbox telling it to reset its master timer
ser.write("e1")
offset=pygame.time.get_ticks()
#Send a message to the bbox telling it to reset its RT sub-timer
ser.write("e5")
#Record how long it took to send the last message
error=pygame.time.get_ticks()-offset
print "Error: %d\n"%error
key=-1
#Loop around and collect responses until the '0' button is pressed
while key != 4:
ser.flushInput()
print "Waiting..."
#Wait for a message from the bbox saying a button got pressed
s=ser.read(6)
print "Message received"
#Record the time, according to the CPU, since the bbox's RT timer was last
reset
#This should equal the time from reset to the button press (the RT), PLUS
the time
#it took to get the message from the bbox to the computer (typically 10-20
ms)
elapsed=pygame.time.get_ticks()-offset
#The first character of the message from the button box is always 'k' -- we
can ignore it.
#The second character of the message
#indicates which button was pressed
key,down=byteToKey(s[1])
#The remaining four characters, converted to base-256 digits, indicate the
RT.
bboxtime=(256^3)*ord(s[5])+(256^2)*ord(s[4])+256*ord(s[3])+ord(s[2])
#Compare the CPU's measurement to the bbox's measurement
discrepancy=elapsed-bboxtime
print "%d %d %d %d %d %d"%(key,down,bboxtime,elapsed,
discrepancy,
error)
#Tell the bbox to reset its RT timer, and record the time we're sending the
message,
#and how long it takes to send the message.
offset=pygame.time.get_ticks()
ser.write("e5")
error=pygame.time.get_ticks()-offset
On Aug 2, 2007, at 6:59 AM, Christophe Pallier wrote: Hello, |
