write_i2c_block_data - how to convert decimal to i2c bytes

Question

I cant find the solution to get this running.

I just want to convert x Seconds to byte and send it via i2c

This is what i tried so far:

off_timer_byte = format(5, '#04x'); #convert decimal to i2c bytes
# also tried this
off_timer_byte = hex(5); #convert decimal to i2c bytes


bus.write_i2c_block_data(address, 0x00, [0x10, off_timer_byte])

The variable "off_timer_byte" can range von 0 to 256. These are seconds to shut down a i2c device after x seconds.

I get this Error:

pi@raspberrypi ~ $ sudo python off.py
Traceback (most recent call last):
  File "off.py", line 48, in <module>
    bus.write_i2c_block_data(address, 0x00, [0x10, off_timer_byte])
TypeError: Third argument must be a list of at least one, but not more than 32 integers

but

bus.write_i2c_block_data(address, 0x00, [0x10, 0x2])

or

bus.write_i2c_block_data(address, 0x00, [0x10, 0x19])

works fine.

Where is the problem?

Thanks so far! ;-)

Joel Gibson · Accepted Answer · 2014-09-03 00:19:43Z

1

The format and hex commands you are using will give you a string that contains '0x05' or '0x5' respectively.

What you need to output into the third argument is a integer value.

Provided your number is below 255, you can simply input that in the list. Otherwise you will need to use bit shifting to split the longer number into two bytes (be careful here with what your slave reads as MSB or LSB first).

answered Sep 3, 2014 at 0:19

Joel Gibson

2932 silver badges8 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

write_i2c_block_data - how to convert decimal to i2c bytes

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related