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NicolasC
Joined: 14 Sep 2006
Posts: 27
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| MAX6956 : Led driver troubles |
 Posted: Sun Jan 14, 2007 3:55 pm |
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Hi,
I have trouble controlling a MAX6956 as led driver.
When port is configured as GPIO I have no problems for reading and writing ports.
But when configured as led driver I can't sink any current. I replace the led with a pullup resistor but still get the same behaviour.
With GPIO output I can light the led (but of course no current control).
No success either with "Display test" function.
Here is my code. Any hint welcome.
| Code: |
enum keypad_state {
IDLE,
OUTPUT_COL
};
#define Port_12_19 0x4C
#define _TEMPO_ 0xFFFF
#define WRITE_ADDR (device_address<<1) & 0xFE
#define READ_ADDR (device_address<<1) | 0x01
int device_address;
typedef int key_cde;
static int16 tempo = _TEMPO_;
static keypad_state mfd_state = IDLE; //machine state for port operation
void write_port(int PortNum, Data)
{
disable_interrupts(GLOBAL);
i2c_start();
i2c_write( WRITE_ADDR );
i2c_write( PortNum );
i2c_write( Data );
i2c_stop();
enable_interrupts(GLOBAL);
}
// Initialise the I2C bus and config register
void mfd_init(int addr )
{
int i;
printf("\r\nI2C init");
addr+= 0x40; //MAX6956 addresses take the form 100xxxx
device_address = addr; //where xxxx is the user-selected address 0-15.
i2c_start();
i2c_write( WRITE_ADDR );
i2c_write( 0x02 ); //Select @02 : Global current config register
i2c_write( 0x0F ); //Set 12mA
i2c_write( 0x00 ); //@03 empty byte
i2c_write( 0x01 ); //@04 Set config register (Transition disable, Global current, no shutdown)
i2c_stop();
//configure port 12 to 22
i2c_start();
i2c_write( WRITE_ADDR );
i2c_write( 0x0B ); //select @0x0B : P15, P14, P13, P12 port config register
i2c_write( 0x00 ); //@0x0B : set Led driver (0x00) // GPIO Output(0x55)
i2c_write( 0x00 ); //@0x0C : P19, P18, P17, P16 : set Led driver (0x00) // set GPIO Output
i2c_stop();
/*
//configure test LED
i2c_start();
i2c_write( WRITE_ADDR );
i2c_write( 0x07 ); //select @0x0B : P15, P14, P13, P12 port config register
i2c_write( 0x01 ); //@0x07 : set Display test
i2c_stop();
*/
mfd_state = OUTPUT_COL;
printf("\r\nI2C init done");
}
int mfd_task(void){
static int is;
switch (mfd_state) {
case IDLE :
mfd_init(0);
break;
default:
if (! --tempo) {
tempo = _TEMPO_;
if ( is ) {
getc();
write_port( Port_12_19, 0x00 /*0b01010101*/ );
is = 0;
printf("\n\rLeds on");
} else {
getc();
write_port( Port_12_19, 0xFF /*0b10101010*/ );
is = 1;
printf("\n\rLeds off");
}
return 1;
} else
return 0;
}
}
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Regards |
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Kenny
Joined: 07 Sep 2003
Posts: 173
Location: Australia
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| Posted: Sun Jan 14, 2007 6:59 pm |
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I haven't used this chip, but noticed the following:
Do you have the recommended 39k resistor connected from ISET to GND to set the maximum segment current?
If so, I think that 0x07 would the value for setting 12mA for all leds.
Also, I think that 0xFF would turn on the leds in the write_port() function. |
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NicolasC
Joined: 14 Sep 2006
Posts: 27
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| Posted: Mon Jan 15, 2007 1:07 am |
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Yes 39k... But connected to the VCC.  ... And I was looking for software problem.
| Quote: | | If so, I think that 0x07 would the value for setting 12mA for all leds. |
You 're right : I've tried different values and now the comment is outdated.
Thanks for your help. |
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