Need help with reading from i2c bus

[Martin L. (tempusertempuser)]

Hello,

how can i read out my i2c device?

the definition is

Command
0xD0
arrayfield 0 first 8bit
arrayfield 1 last 8bit

[Andreas B. (bitverdreher)]

This is in depend what's written in the datasheet of your secret I2C 
device.

[Martin L. (tempusertempuser)]

here is the datasheet

https://forum-raspberrypi.de/attachment/12257-susvpi-manual-rev1-4-ger-pdf/

[Andreas B. (bitverdreher)]

Send first the device address and the command:
0x0F 0xD0
then read the both bytes

[Martin L. (tempusertempuser)]

How can I do this with python and later than also fit the two bytes 
together??

I am lost in the jungle

[Andreas B. (bitverdreher)]

https://letmegooglethat.com/?q=python+i2c

General you should learn the programming language before what you want 
to use.
This forum is not a programming service.

[Martin L. (tempusertempuser)]

Andreas B. schrieb:
> https://letmegooglethat.com/?q=python+i2c
>
> General you should learn the programming language before what you want
> to use.
> This forum is not a programming service.

This is my try but the result this wrong

#!/usr/bin/python3
import smbus
import requests
import time

bus = smbus.SMBus(1)
address = 0x0F
x = bus.read_i2c_block_data(address, 0xD0,3)
voltagein = x[2] <<8 | (x[1])
#print (x[1])
#print (x[2])

voltagein_string = "%i" % voltagein
print  (voltagein_string)
bus.close()
del x
del bus

[Matthias S. (Firma: matzetronics) (mschoeldgen)]

Martin L. schrieb:
> voltagein = x[2] <<8 | (x[1])
Try:

voltagein  = (x[0] * 256) + x[1]

[Martin L. (tempusertempuser)]

Matthias S. schrieb:
> Martin L. schrieb:
>> voltagein = x[2] <<8 | (x[1])
> Try:
>

> voltagein  = (x[0] * 256) + x[1]
>

This prints 2 times the same value

bus = smbus.SMBus(1)
address = 0x0F
x = bus.read_i2c_block_data(address, 0xD0,2)
print ("x")
print (x)
#voltagein = (x[1]<<8) | (x[0])
voltagein  = (x[0] * 256) + x[1]
voltagein_string = "%i" % voltagein
print ("voltage in")
print (voltagein)
bus.close()
del x
del bus

time.sleep(2)
bus = smbus.SMBus(1)
address = 0x0F
x = bus.read_i2c_block_data(address, 0xD1,2)
print ("x")
print (x)
#powerextern = x[0] | (x[1]<<8)
powerextern = (x[0] * 256) + x[1]
pwerextern_string = "%i" % powerextern
print ("powerstring")
print (pwerextern_string)
bus.close()
del x
del bus

x
[208, 137]
voltage in
53385
x
[209, 132]
powerstring
53636

[Matthias S. (Firma: matzetronics) (mschoeldgen)]

Does look right for a 48V System.

[Martin L. (tempusertempuser)]

but it should be ~5V

[Hmmm (hmmm)]

Martin L. schrieb:
> x
> [208, 137]

Martin L. schrieb:
> x
> [209, 132]

Seems like the first byte is always the command. What does your debug 
output look like after reading 3 bytes?

[Martin L. (tempusertempuser)]

Hmmm schrieb:
> Martin L. schrieb:
>> x
>> [208, 137]
>
> Martin L. schrieb:
>> x
>> [209, 132]
>
> Seems like the first byte is always the command. What does your debug
> output look like after reading 3 bytes?

[sudo] password for openhabian: 
x
[208, 126, 20]
voltage in
53374
x
[209, 159, 20]
powerstring
53663

[Hmmm (hmmm)]

Martin L. schrieb:
> [208, 126, 20]

powerextern = (x[2] * 256) + x[1]

[Martin L. (tempusertempuser)]

Martin L. schrieb:
> Hmmm schrieb:
>> Martin L. schrieb:
>>> x
>>> [208, 137]
>>
>> Martin L. schrieb:
>>> x
>>> [209, 132]
>>
>> Seems like the first byte is always the command. What does your debug
>> output look like after reading 3 bytes?
>
>

> [sudo] password for openhabian:
> x
> [208, 126, 20]
> voltage in
> 53374
> x
> [209, 159, 20]
> powerstring
> 53663
> 
>

bus = smbus.SMBus(1)
address = 0x0F
x = bus.read_i2c_block_data(address, 0xD0,9)
print ("x")
print (x)
voltagein = (x[2]<<8) | (x[1])
#voltagein  = (x[1] * 256) + x[2]
voltagein_string = "%i" % voltagein
print ("voltage in")
print (voltagein)
bus.close()
del x
del bus

time.sleep(2)
bus = smbus.SMBus(1)
address = 0x0F
x = bus.read_i2c_block_data(address, 0xD1,9)
print ("x")
print (x)
powerextern = (x[3]<<8) | x[2]
#powerextern = (x[0] * 256) + x[1]
pwerextern_string = "%i" % powerextern
print ("powerstring")
print (pwerextern_string)
bus.close()
del x
del bus

x
[208, 110, 20, 1, 105, 20, 0, 0, 0]
voltage in
5230
x
[209, 143, 20, 1, 105, 20, 0, 0, 0]
powerstring
276

[Martin L. (tempusertempuser)]

Hmmm schrieb:
> Martin L. schrieb:
>> [208, 126, 20]
>
> powerextern = (x[2] * 256) + x[1]

Das sollte rauskommen

********************************
*                              *
* S.USV solutions              *
* www.s-usv.com                *
*                              *
* Model: Advanced              *
* Firmware Version: 2.61       *
* Software Version: 2.40       *
* Hardware Version: 2.2        *
*                              *
* Mail notification: Disabled  *
*                              *
* Timed Boot: Disabled         *
* Boot time: 00:00:00          *
*                              *
* Timed Shutdown: Disabled     *
* Shutdown time: 00:00:00      *
*                              *
* Fri Oct 11 18:18:54 2024     *
*                              *
********************************
*                              *
* Powering Source: Primary     *
* Charging circuit: OFFLINE    *
* Charging current: 300 mA     *
*                              *
* Voltage in: 5.23 V           *
* Battery capacity: 100.00%    *
* Battery voltage: 4.20V       *
* Power Battery: 000.00 mA     *
* Power Extern: 1259.00 mA      *
*                              *
* Shutdown timer: -1           *
* Autostart:  enabled          *
* Sleep timer: 1               *
*                              *
********************************

[Hmmm (hmmm)]

Martin L. schrieb:
> voltage in
> 5230

5230 mV = 5.230 V

The device seems to send the command byte followed by the low byte and 
the high byte of the value, so just use (x[2] * 256) + x[1] in both 
cases.

[Martin L. (tempusertempuser)]

Hmmm schrieb:
> Martin L. schrieb:
>> voltage in
>> 5230
>
> 5230 mV = 5.230 V
>
> The device seems to send the command byte followed by the low byte and
> the high byte of the value, so just use (x[2] * 256) + x[1] in both
> cases.

there is no difference between the commands

bus = smbus.SMBus(1)
address = 0x0F
x = bus.read_i2c_block_data(address, 0xD0,3)
print ("x")
print (x)x
[208, 132, 20]
voltage in
5252
x
[209, 126, 20]
powerstring
5246

voltagein = (x[2]<<8) | (x[1])
#voltagein  = (x[1] * 256) + x[2]
voltagein_string = "%i" % voltagein
print ("voltage in")
print (voltagein)
bus.close()
del x
del bus

time.sleep(2)
bus = smbus.SMBus(1)
address = 0x0F
x = bus.read_i2c_block_data(address, 0xD1,3)
print ("x")
print (x)
#powerextern = (x[3]<<8) | x[2]
powerextern = (x[2] * 256) + x[1]
#powerextern = (x[0] * 256) + x[1]
pwerextern_string = "%i" % powerextern
print ("powerstring")
print (pwerextern_string)
bus.close()
del x
del bus

x
[208, 132, 20]
voltage in
5252
x
[209, 126, 20]
powerstring
5246

[Matthias S. (Firma: matzetronics) (mschoeldgen)]

There are 3 bytes in the response. First byte is the command and can be 
ignored.
The second byte is the LSB and the third byte is the MSB.
So

voltage = (x[2] * 256) + x[1]

and

voltage = (x[2] << 8) | x[1]

should give the same results

[Andreas B. (bitverdreher)]

I miss the initialyze of the I2C bus.

[Martin L. (tempusertempuser)]

Andreas B. schrieb:
> I miss the initialyze of the I2C bus.

How do I do this?

[Matthias S. (Firma: matzetronics) (mschoeldgen)]

Martin L. schrieb:
> How do I do this?

Never mind, an initialization is obviously already there. Otherwise you 
wouldn't get any results from the I²C bus.

bus = smbus.SMBus(1)