### Author:  [@vasja](https://forums.openmv.io/u/vasja)
#### Post date: [May 23, 2021, 6:46pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/1 "2021-05-23T18:46:22Z")
Hello, dear collegues!
I use the OpenMV H7 board and want to work with CAN.
I try to work with the CAN example that is in examples menu but it does not work.
Then I try to write my prog and my first command is:
import time, omv
from pyb import CAN
I try to compile it and there is a message – “ImportError: cannot import name CAN”.
Where is mistake?
Can you help me with some small Tx/Rx example?
---
### Author:  [@kwagyeman](https://forums.openmv.io/u/kwagyeman)
#### Post date: [May 24, 2021, 1:18am UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/2 "2021-05-24T01:18:29Z")
@iabdalkader
>
Is not working…
---
### Author:  [@vasja](https://forums.openmv.io/u/vasja)
#### Post date: [December 17, 2021, 1:20pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/3 "2021-12-17T13:20:30Z")
Now I work with the canbus, and its working in the Lopback mode:
import sensor, image, time, pyb, json, omv
from pyb import CAN
clock = time.clock()
can = CAN(2, CAN.LOOPBACK)
can.setfilter(0, CAN.RANGE, 0, (1, 4))
while(True):
clock.tick()
can.send(‘mege!’, 2)
time.sleep\_ms(100)
print(can.recv(0))
Now I try to work in the Normal mode, but there is some problem.
Could you help me to to find the problem in my code, that is attached bellow?
import sensor, image, time, pyb, json, omv
from pyb import CAN
clock = time.clock()
#canbus communication config
can = pyb.CAN(2, CAN.NORMAL)
can.init(pyb.CAN.NORMAL, extframe=False, prescaler=18, sjw=1, bs1=8, bs2=3) #250kb/s
while(True):
clock.tick()
can.send(15, 0x123,timeout=1000, rtr=False) # send a message with id 123
time.sleep\_ms(100)
---
### Author:  [@kwagyeman](https://forums.openmv.io/u/kwagyeman)
#### Post date: [December 17, 2021, 6:18pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/4 "2021-12-17T18:18:10Z")
Do you have a phy attached and another device sending data?
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### Author:  [@vasja](https://forums.openmv.io/u/vasja)
#### Post date: [December 17, 2021, 6:37pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/5 "2021-12-17T18:37:19Z")
Yes, I have STM32 based controller, I try to send data from h7 to the controller and back. I use iso1050dub can transceiver.
---
### Author:  [@vasja](https://forums.openmv.io/u/vasja)
#### Post date: [March 14, 2022, 7:09am UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/6 "2022-03-14T07:09:05Z")
Is somwhere the code example where the CAN bus with callback is used? The problem is: monitor what is in the CAN bus but not in the main program.
---
### Author:  [@vasja](https://forums.openmv.io/u/vasja)
#### Post date: [March 14, 2022, 10:28am UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/7 "2022-03-14T10:28:43Z")
import sensor, image, time, array, pyb, omv
from pyb import LED
from pyb import CAN
sensor.reset()
sensor.set\_pixformat(sensor.RGB565) # grayscale is faster
sensor.set\_framesize(sensor.QQVGA)
sensor.skip\_frames(time = 1000)
clock = time.clock()
can = CAN(2, CAN.NORMAL, baudrate=125\_000, sample\_point=75)
can.restart()
FLAG\_Work = 100
red\_led = LED(1)
green\_led = LED(2)
blue\_led = LED(3)
ir\_led = LED(4)
i=0
int\_array1 = array.array(‘i’, [1, 2, 3])
int\_array2 = array.array(‘i’, [1, 2, 3])
def cb0(bus, reason):
print(‘cb0’)
if reason == 0:
print(‘pending’)
FLAG\_Work = 200
if reason == 1:
FLAG\_Work = 200
print(‘full’)
if reason == 2:
print(‘overflow’)
FLAG\_Work = 200
can.setfilter(0, CAN.RANGE, 0, (10, 30))
can.rxcallback(0, cb0)
while(True):
clock.tick()
img = sensor.snapshot()
print(can.rxcallback(0, fun))
#can.rxcallback(0, cb0)
if FLAG\_Work == 100:
for c in img.find\_circles(threshold = 3400, x\_margin = 5, y\_margin = 10, r\_margin = 10, r\_min = 6, r\_max = 15, r\_step = 2):
img.draw\_circle(c.x(), c.y(), c.r(), color = (255, 0, 0))
if i \< len(int\_array1):
int\_array1[i] = c.x()
int\_array2[i] = c.y()
i=i+1
#pyb.delay(500)
else:
i = 0
#print(c)
i = 0
print(“FPS %f” % clock.fps())
My code is here but callback does not work. I think that I do something wrong but i do not know where is mistake… Please, help with this problem…
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### Author:  [@kwagyeman](https://forums.openmv.io/u/kwagyeman)
#### Post date: [March 15, 2022, 12:57pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/8 "2022-03-15T12:57:42Z")
Please format your code.
---
### Author:  [@vasja](https://forums.openmv.io/u/vasja)
#### Post date: [March 15, 2022, 7:02pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/9 "2022-03-15T19:02:44Z")
```auto
import sensor, image, time, array, pyb, omv
from pyb import LED
from pyb import CAN
sensor.reset()
sensor.set_pixformat(sensor.RGB565) # grayscale is faster
sensor.set_framesize(sensor.QQVGA)
sensor.skip_frames(time = 1000)
clock = time.clock()
can = CAN(2, CAN.NORMAL, baudrate=125_000, sample_point=75)
can.restart()
FLAG_Work = 100
red_led = LED(1)
green_led = LED(2)
blue_led = LED(3)
ir_led = LED(4)
i=0
int_array1 = array.array(‘i’, [1, 2, 3])
int_array2 = array.array(‘i’, [1, 2, 3])
def cb0(bus, reason):
print(‘cb0’)
if reason == 0:
print(‘pending’)
FLAG_Work = 200
if reason == 1:
FLAG_Work = 200
print(‘full’)
if reason == 2:
print(‘overflow’)
FLAG_Work = 200
can.setfilter(0, CAN.RANGE, 0, (10, 30))
can.rxcallback(0, cb0)
while(True):
clock.tick()
img = sensor.snapshot()
print(can.rxcallback(0, fun))
#can.rxcallback(0, cb0)
if FLAG_Work == 100:
for c in img.find_circles(threshold = 3400, x_margin = 5, y_margin = 10, r_margin = 10, r_min = 6, r_max = 15, r_step = 2):
img.draw_circle(c.x(), c.y(), c.r(), color = (255, 0, 0))
if i < len(int_array1):
int_array1[i] = c.x()
int_array2[i] = c.y()
i=i+1
#pyb.delay(500)
else:
i = 0
#print(c)
i = 0
print(“FPS %f” % clock.fps())
```
---
### Author:  [@vasja](https://forums.openmv.io/u/vasja)
#### Post date: [March 17, 2022, 1:59pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/10 "2022-03-17T13:59:02Z")
Formated it!
---
### Author:  [@kwagyeman](https://forums.openmv.io/u/kwagyeman)
#### Post date: [March 19, 2022, 9:18pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/11 "2022-03-19T21:18:09Z")
Can you verify the filter you set is actually working?
---
### Author:  [@vasja](https://forums.openmv.io/u/vasja)
#### Post date: [May 11, 2022, 11:27am UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/12 "2022-05-11T11:27:44Z")
Now it works but when it is connected through the openmv ide. when I disconnect it, it does not work (supply is good). May be I forgot some part of code? The code is uploaded as main.py.
```
import sensor, image, time, array, pyb, omv
from pyb import CAN
sensor.reset()
sensor.set_pixformat(sensor.RGB565) # grayscale is faster
sensor.set_framesize(sensor.QQVGA)
sensor.skip_frames(time = 1000)
clock = time.clock()
can = CAN(2, CAN.NORMAL, baudrate=125_000, sample_point=75)
can.setfilter(0, CAN.RANGE, 0, (1, 3))
can.restart()
FLAG_Work = 200
FLAG_BIGMARK = 0
i=0
int_array1 = array.array('i', [1, 2, 3])
int_array2 = array.array('i', [1, 2, 3])
x_coordinates = array.array('i', [1, 2, 3])
y_coordinates = array.array('i', [1, 2, 3])
rmin = 6
while(True):
clock.tick()
img = sensor.snapshot().lens_corr(strength = 1, zoom = 1.0)
while(can.any(0)):
message = can.recv(0)
print(message[0])
if(message[0] == 0x1):
FLAG_Work = 100
print('YES')
if(message[0] == 0x3):
FLAG_Work = 200
print('NOT')
if FLAG_Work == 100:
for c in img.find_circles(threshold = 3400, x_margin = 5, y_margin = 10, r_margin = 10, r_min = rmin, r_max = 20, r_step = 2):
img.draw_circle(c.x(), c.y(), c.r(), color = (255, 0, 0))
if c.r() > 10:
rmin = 12
x_coordinates[0] = 250
x_coordinates[1] = c.x()
x_coordinates[2] = 250
y_coordinates[0] = 240
y_coordinates[1] = c.y()
y_coordinates[2] = 240
FLAG_BIGMARK = 100
else:
if i < 3:
int_array1[i] = c.x()
int_array2[i] = c.y()
i=i+1
FLAG_BIGMARK = 200
else:
i = 0
i = 0
if FLAG_BIGMARK == 200:
x_coordinates = sorted(int_array1)
y_coordinates = sorted(int_array2)
can.send(bytes(x_coordinates+y_coordinates), 0x112)
int_array1[0]=255
int_array1[1]=255
int_array1[2]=255
int_array2[0]=254
int_array2[1]=254
int_array2[2]=254
```
---
### Author:  [@kwagyeman](https://forums.openmv.io/u/kwagyeman)
#### Post date: [May 12, 2022, 4:16pm UTC](https://forums.openmv.io/t/canbus-openmv-h7/5921/13 "2022-05-12T16:16:49Z")
Did you save the script to the OpenMV Cam and then safety eject the device?