Multi-digit word variable to string

[richard]

I found this,if i remember correctly somewhere related to this specific sensor.


Code:
tempir = (temp.highbyte << 8) + temp.lowbyte

maybe but in conjunction with
i2cread SDA, SCL,addr,reg,[temp.lowbyte,temp.highbyte] ' reg = $07

its not useful in any way

Now what is wrong with the I2C command?

all this achieves is exactly nothing

reg    = $07             ' based on the datasheet $07 is the object's temp


grave doubts about all of this  it looks like some mishmash of a C code method where no read/write register command exists as it does in pbp 
addr   = %10110100       ' $B4  binary value: %10110100
i2cwrite SDA, scl, addr  ' send write command, shift the address B4, 8 bits where LSB is W = 0
i2cwrite sda, scl, reg   ' register is $07


i2cwrite sda, scl, addr,reg, [some data of some sort]  ' register is $07 ;would be the normal way if you had any data to write 


totally bogus in pbp bit 0 should always be 0
addr   = %10110101       ' $B5  Binary value: %10110101


a form of torture to i2c chips with an incomplete transaction
i2cwrite sda, scl, addr  ' sends read command, shift the address B5, 8 bits where LSB is R = 1, clock idles low

all that's needed
reg = $07
addr = %10110100
i2cread SDA, SCL,addr,reg,[temp.lowbyte,temp.highbyte] ' reg = $07 ;would be the normal pbp way

[astanapane]

Richard,

now i got a bit comfused. If i only add the following, it doent work as expected

all that's needed
reg = $07
addr = %10110100
i2cread SDA, SCL,addr,reg,[temp.lowbyte,temp.highbyte] ' reg = $07 ;would be the normal pbp way

But if i add the write mode and I2Cwrite command it works.

reg = $07 ' this is the register for IR temp mode
addr= %10110100 ; this is the write mode

i2cwrite SDA, SCL, addr 
i2cread SDA, SCL, addr, reg, [TEMP.lowbyte, TEMP.highbyte]

the following also works.

reg = $07 ' this is the register for IR temp mode
addr= %10110100 ; this is the write mode
i2cwrite SDA, SCL, addr 

addr= %10110101 ; this is the read mode
i2cread SDA, SCL, addr, reg, [TEMP.lowbyte, TEMP.highbyte]

if i do not add the following line the code doesnt work.

i2cwrite SDA, SCL, addr

Shouldnt we write first and then read? ok i understand that we have nothing to write. But why it doent work if i do not add the i2cwrite line?

[richard]

Shouldnt we write first and then read? ok i understand that we have nothing to write. But why it doent work if i do not add the i2cwrite line?

which is precisely what the i2cread command does for you automatically. it should not ever be necessary to add a extra write , no i2c chip i have ever encountered has needed such treatment

i2cwrite SDA, SCL, addr

is an incomplete transaction. if your chip needs it then it is not a true i2c device or something else is occurring.
a logic analyzer would show what's really happening. its not normal and should be examined further to have any confidence
that the code is really viable in the long term

addr = %10110100

trying to set bit0 [the r/w bit] of a i2c address with pbp's i2c commands is not possible and will not have any effect
the code will set the r/w bit as needed

[richard]

it could be the chip is not really i2c and behaves differently

try this, at least its a nicer transaction
i2cwrite SDA, SCL, addr,[7]
i2cread SDA, SCL, addr,[TEMP.lowbyte, TEMP.highbyte]



looking at the wiki link you posted, this would do exactly what the smbus timing diagram describes as a proceedure

PEC var byte
i2cread SDA, SCL,addr,reg,[temp.lowbyte,temp.highbyte,PEC] ' reg = $07 ;would be the normal pbp way

worth trying

[astanapane]

Hi Richard,

sure i'll try that, and i will try to figure out what is going on with a logic analyzer.

I have a saleae logic 8.

Will try that later today. Many thanks for your time once again.

[richard]

If there is only one MLX90614 sensor, the 7-bits address is 0x00 by default.

according to wiki addr =0 where did you get B4 from ?

[Ioannis]

If the chip is the MAX30102, on page 16 seems that reading needs first a write.

Ioannis

[astanapane]

If the chip is the MAX30102, on page 16 seems that reading needs first a write.

Ioannis

it is an IR MLX90614

[astanapane]

wait a sec,

im reading the manual again from the SENSOR

https://www.waveshare.com/w/upload/e/e4/MLX90614-EN.pdf