ATmega32 Controlling DS1802 pot

[fbee]

Hi,
there are some threads on controlling DS1802 with IR or Rotary encoders. I Plan to command the DS1802 with RS232 commands (out of a linn Player).
Now , the ATmega has an SPI out , that could Control the 3wire Serial Input of the DS1802 (RST, CLK, D Inputs).
Can anyone help me, how to generate the Serial commands in the ATmega32, that the DS needs to see?
Thanks a Lot, Frank

[ratza]

You can simply send raw hex values over serial communication, copy the two bytes in some local variables and then send them over SPI. Be carefull with DS1802, since it has the chip select line active on high level and the bytes are sent with LSB first.

[fbee]

Thanks,

as it´s my first uC project, I just wonder if I have to take care, that RST is "high" while the hexcode is sent and so on. In the datasheet of the DS1802 the serial controlling seems sooo complicated with the tcc, tch .... timing and the clocksynchronisation.

Is it that simple, just connecting the clock out of the ATmega (XCK pin#1) to the CLK (pin#3) of the DS1802?

Furthermore I would connect
SCK on the ATmega (pin#7) to D(pin#4) on DS1802,
SS on the ATmega (pin#4) to RST(pin#5) on DS1802
GND to GND.

...or am I missing something?

Frank

[Sci]

You might get more help on avrfreaks.net, a site dedicated to AVR programming.

[theAnonymous1]

Just curious, why the DS1802? It will need an additional buffer circuit and the signal will be limited by the 5V supply.

It's a novel circuit to play with if your just going to use push buttons, but if you plan to put the effort into using a uC then there are better IC's available.

[fbee]

DS1802 because it´s used on the VCCS board for the Lightspeed attenuator, that I build.

The uC would translate the ASCII strings, that come out of the networkplayer, into commands for volume setting (and poweramp control by 12V toggle)

My Ipod with PlugPlayer is an upnp controlpoint of the networkplayer and it uses a slider for Volume setting. So, when I move the slider to 87% volume, the networkplayer sends a command $Volume=87$ (the value is between 0 and 100) as ASCII code to the uC (UART RX).

The uC would recognise the volume command and the value after the "=" and multiply the value by 0,64 (as the DS1802 pointer has 64 steps). Then the uC would somehow?? generate the serial commands for the RST , D and CLK inputs of the DS1802.

[theAnonymous1]

Ah, ok. So the signal won't be passing through the DS1802, it's just used to control the optocouplers.

Makes sense now.

[sasmit]

first you need to look at ATMEL documentation for TWI interface, there is an AVR document for ..how to's of TWI.
You can also have a look at the documentation of IC's like TDA7449 that use the TWI inteface for controlling. The datasheet of TDA 7449 in fact carries a lot of information regarding how to send signals over TWI and how to send address etc.
Have a look at this also www.atmel.com/dyn/resources/prod_documents/doc2564.pdf

[ratza]

Originally Posted by fbee

Furthermore I would connect
SCK on the ATmega (pin#7) to D(pin#4) on DS1802,
SS on the ATmega (pin#4) to RST(pin#5) on DS1802
GND to GND.

Connections are as following:
D (pin 4) goes to MOSI (pin 6)
CLK (pin 3) goes to SCK (pin 8)
RST (pin 5) goes to SS (pin 5) or any other port pin you like to use as chip select line.
The power supply can be the same for both ATmega and DS.

Flow of the code:
- register initialization (system clock, ports, USART, SPI);
- infinite loop in which data is received over USART and sent over SPI.

I think this thread can be placed better in Digital Line Level section of the forums.

[fbee]

Ratza,
thanks this was very helpful.
I´ll try that route.
Cheers, Frank