I2C virtual peripheral

Alessandro

Hi guys how are you?
·I'm fine, i'm just work around the I2C virtual peripheral to comunicate with·the LEGO ULTRASONIC sensor (of NXT).

I have some problem...

I'm trying to reproduce the normal I2C·comunication of the NXT brick with an SX28.

It follows the I2C standard. but in the comunication there is a byte (the third) that i can't send with sx.

I need to send a simple byte: a "00000011" and then the slave (the ultrasonic sensor) has to respond me with an ack.

Can Anybody help me?

Thanks a lot!

Alessandro Italy

Bean

Alessandro,
Please post what you have so far.
It should be just I2CSEND SDA, %00000011

Bean.

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Alessandro

I'm using Scenix Virtual peripheral, i2cm_vp.src .

I'm programming in Assembler
but if you have some other working in SX/B i'm happy to use it.

Next step is to use the SX as slave connected to the NXT brick (that is only master in I2C comunication)

Bean

Oh I missed that you were using the VP.
Post the code anyway.

Bean.

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Alessandro

This is my MAIN (the rest of VP in not changed appart for the slaveid and the isr_period)

I need to Send the byte in this order (1° slaveid, address of memory, $03, and then i need to read the result of a distance misure by Lego Ultrasonic Sensor.

Can anybody help? or send me the routin in SXB?



main _bank I2CM
mov I2CM_address,#slave_adr ; set address of slave to read.
_bank VARS ; clear read and write pointers
clr read_adr
clr write_ptr
mov read_adr,#$42

I2C_read
_bank VARS
mov w,read_adr
_bank I2CM
mov I2CM_data_0,w ; load send register with data address
call @I2CM_wait_not_busy ; wait for I2CM state machine to enter idle state
call @I2CM_send_byte ; send 'want to read' and bank addess to i2c slave
call @I2CM_wait_not_busy ; wait for I2CM state machine to enter idle state
call @I2CM_get_byte ; Gets the byte from slave and returns it in w
snb I2CM_NACK
jmp got_NACK ; indicate no NACK by entering never ending loop
test w ; check for null character read
;jz main ; null char, end of string...restart
;mov recv_char,w ; save received character
;cjne recv_char,#'S',bad_data ; used to confirm valid recieved matches stored data


Thanks a lot.

Alessandro (Italy)

Alessandro

the sequence i'd like to reproduce is:
Slaveid( in my case $02), address memory of slave (in my case $42), $03, and then i'd like to read the result of measurament.
Any idea of prolem in my code?

Thanks
Alessandro (Italy)

Sparks-R-Fun

Alessandro,

I only see one call to I2CM_send_byte but you describe a need to send three bytes before you perform a read operation.· Where are you trying to send each of the bytes you describe?

·- Sparks

Alessandro

Hi Sparks-R-Fun

In the first lines, i·wrote the SLAVEid and the address of slave:

mov I2CM_address,#slave_adr······················ ; set address of slave to read.
_bank VARS ; clear read and write pointers
clr read_adr
clr write_ptr
mov read_adr,#$42
If you see with oscilloscope, you will find that this two byte are send·on the SDA line of I2C with one call.
The third byte is sent with another call,that i Added:

_bank·I2CM
··mov·I2CM_data_0,#$03··;load send register with data address
··call·@I2CM_wait_not_busy··; wait for I2CM state machine to enter idle state
··call·@I2CM_start_write··; wait for I2CM state machine to enter idle state
··call·@I2CM_write···; send 'want to read' and bank addess to i2c slave
··call·@I2CM_wait_not_busy··; wait for I2CM state machine to enter idle state
··;call·@I2CM_get_byte

··;snb·I2CM_NACK
··;jmp·got_NACK···; indicate no NACK by entering never ending loop
··test·w····; check for null character read
··;jz·main····; null char, end of string...restart
··mov·recv_char,w···; save received character
··;cjne·recv_char,#'S',bad_data··; used to confirm valid recieved matches stored data

The problem is that between the first 2 byte and the third there is (seen with oscilloscope) another byte that it is not on the· code i write.

In this way the LEGO NXT sensor will not work.

What are the problems in my code?
Has someone the SASM traslation of this assembly virtual peripheral?

Thanks for answer.
Alessandro

Alessandro

ANY who uses the i2c virtual peripheral..... please....

Alessandro Leopardi