I2C seems broken with LTC4151 and nodemcu
Posted: Fri Dec 18, 2015 8:05 amHi,
hopefully this is the right place to post. I'm currently struggling to get communication going with an LTC4151 current- and voltage-monitor. Scanning the I2C-bus I get a reply on the expected address. However if I'm reading on the registers for current, voltage and auxiliary voltage I always get the same result no matter what voltage is applied to the ADC. Here's a link to the datasheet of that chip: http://cds.linear.com/docs/en/datasheet/4151ff.pdf
Also setting the control-register seems to work, but I cannot read it back. Always getting 0es.
Have a look at my test-code:
After starting up the esp-module, I entered the following:
As you can see, I always get back 0 and 240 (0x00 for msb and 0xf0 for lsb).
Now look at the ltctest carefully: first I'm setting the control-register to 0x04 (test-mode). In this mode you should be able to set arbitrary values to the ADC-registers. I'm setting register 0x00 and 0x01! After that, I'm reading back register 0x02 and 0x03!! And there I'm getting the expected values. Reading back 0x00/01 I still get the 0x00 and 0xf0 values. Something is messed up there.
Finally I already did read that chip successfully on an Atmega 8. The only difference in the code to me is, that I'm doing a repeated-start after writing the register I want to read. In Lua I have to make a i2c.stop, i2c.start and i2c.address with RECEIVER-option set.
Any ideas on how I can get down to the problem? Unfortunately I'm not blessed with a memory oscilloscope. So I can't actually look into the bus or timings
Appreciate your help!
hopefully this is the right place to post. I'm currently struggling to get communication going with an LTC4151 current- and voltage-monitor. Scanning the I2C-bus I get a reply on the expected address. However if I'm reading on the registers for current, voltage and auxiliary voltage I always get the same result no matter what voltage is applied to the ADC. Here's a link to the datasheet of that chip: http://cds.linear.com/docs/en/datasheet/4151ff.pdf
Also setting the control-register seems to work, but I cannot read it back. Always getting 0es.
Have a look at my test-code:
Code: Select all
gpiolookup = {[0]=3,[1]=10,[2]=4,[3]=9,[4]=1,[5]=2,[10]=12,[12]=6,[13]=7,[14]=5,[15]=8,[16]=0}
ltc4151 = 0x6f
-- setup I2c
function init_i2c()
-- SDA and SCL can be assigned freely to available GPIOs
local sda = gpiolookup[0] -- GPIO0
local scl = gpiolookup[2] -- GPIO2
i2c.setup( 0, sda, scl, i2c.SLOW )
end
function getI2C( address )
local rec
local msb = 0
local lsb = 0
i2c.start( 0 );
i2c.address( 0, ltc4151, i2c.TRANSMITTER )
i2c.write( 0, address )
i2c.stop( 0 )
i2c.start( 0 )
i2c.address( 0, ltc4151, i2c.RECEIVER )
rec = i2c.read( 0, 2 )
i2c.stop( 0 )
msb = string.byte( rec, 1 )
lsb = string.byte( rec, 2 )
print( msb )
print( lsb )
local ret = bit.lshift( msb, 4 ) + bit.rshift( lsb, 4 )
return( ret )
end
function getADC_current()
-- Read current: Address 0x00;
return( getI2C( 0x00 ) )
end
function getADC_usol()
-- Read voltage: Address 0x02;
return( getI2C( 0x02 ) )
end
function getADC_uaux()
-- Read aux-voltage: Address 0x04;
return( getI2C( 0x04 ) )
end
function getControl()
-- Read control register: Address 0x06;
local ret
i2c.start( 0 )
i2c.address( 0, ltc4151, i2c.TRANSMITTER )
i2c.write( 0, 0x06 )
i2c.stop( 0 )
i2c.start( 0 )
i2c.address( 0, ltc4151, i2c.RECEIVER )
ret = i2c.read( 0, 1 )
i2c.stop( 0 )
return( string.byte( ret ) )
end
function setI2C( address, val )
i2c.start( 0 )
i2c.address( 0, ltc4151, i2c.TRANSMITTER )
i2c.write( 0, address, val )
i2c.stop( 0 )
end
function ltctest()
-- enter test mode
setI2C( 0x06, 0x04 )
setI2C( 0x00, 0xaa )
setI2C( 0x01, 0xa0 )
print( getADC_usol() )
-- reset control register
setI2C( 0x06, 0x00 )
end
init_i2c()
After starting up the esp-module, I entered the following:
Code: Select all
> dofile("ltc4151.lua")
> getADC_usol()
0
240
> print( getADC_usol() )
0
240
15
> print( getControl() )
0
> setI2C( 0x06, 0x04 )
> print( getControl() )
0
> ltctest()
170
160
2730
> print( getADC_usol() )
0
240
15
>
As you can see, I always get back 0 and 240 (0x00 for msb and 0xf0 for lsb).
Now look at the ltctest carefully: first I'm setting the control-register to 0x04 (test-mode). In this mode you should be able to set arbitrary values to the ADC-registers. I'm setting register 0x00 and 0x01! After that, I'm reading back register 0x02 and 0x03!! And there I'm getting the expected values. Reading back 0x00/01 I still get the 0x00 and 0xf0 values. Something is messed up there.
Finally I already did read that chip successfully on an Atmega 8. The only difference in the code to me is, that I'm doing a repeated-start after writing the register I want to read. In Lua I have to make a i2c.stop, i2c.start and i2c.address with RECEIVER-option set.
Code: Select all
uint16_t getI2C( uint8_t address ) {
uint8_t msb, lsb;
msb = lsb = 0;
if( i2c_start( LTC4151 + I2C_WRITE ) == 0 ) {
i2c_write( address );
i2c_rep_start( LTC4151 + I2C_READ );
msb = i2c_readAck();
lsb = i2c_readNak();
i2c_stop();
return( ( msb << 4 ) + ( lsb >> 4 ) );
} else {
return( 0 );
}
}Any ideas on how I can get down to the problem? Unfortunately I'm not blessed with a memory oscilloscope. So I can't actually look into the bus or timings
Appreciate your help!