LP55231: LEDs driver does not Turn ON LED lights

Hi Robert,

Could you help to re-post your schematic? It seems died in original thread.

And how you sent I2C commands, GUI or MCU simulation?

I don't know how to attach the image in this forum. I pasted it in the text area. If you send me an email, I can reply with the schematic section.

I have a microcontroller  i2c bus connected to the chip. I wrote c code to communicate with it.

RR

Dear Hardy,

The schematic I sent is for 2 LED drivers.  I have written C-code in a microcontroller to send command via I2C bus to the device.  I have a logic analyzer hooked on the bus monitoring the MCU to ensure the command reach the IC on its bus.  the image attached shows an example capture for some commands I sent.

Here is some "experimental" code I wrote trying multiple things... the code is raw and I have not cleaned up comments, and I am using repetition command rather than doing it properly in the interest of saving time.  I need to understand few things.

1. In the hardware the TRIG pin is hard wired to GROUND.  Is this a problem?

2. The INT pin is floating is this a problem?

3. What should be the proper sequence to turn on the LEDs?  All I want to do is just turn on a RED, GREEN, and BLUE LED connected to my custom hardware.   It would be nice to just have a pseudo code that show how to turn on LEDs without the intricate programs one can do on this chip.  I just want to Turn On, the red, then the green, then the blue.  That is all.  I am just trying to prove the hardware is good, and that the MFG house assembled the chip correctly.

-  I have tried to setup the current, the PWM register, I have initialized several register, and I can see the MCU writing correctly, but the chip is simply unresponsive.

- Visual inspection on the board shows the chips is soldered down correctly, yet no light comes ON.

From my perspective, the LAYOUT is in order, the schematic fairs good with sparkfun breakout board using the LP55231, the only difference between this board and mine is the TRIG pin (which I am not using) being grounded, and INT pin floating.

We are at a loss as to why it refuses to work.  All 25 board are like this, and I refuse to believe the assembly temperature killed all the chips, or that everyone of those chips have cold solders.  It is more likely the code is sending the correct sequence to this part.  This is where I need your assistance.

Best,

RR

#include "CCSUSB.h"
#include <usb_cdc.h>

/*
Initialize MCU I2C1 SSP ENGINE
The PIC24FJ256GB206 has its SDA1, SCL1 on
SCL1 = TQFP-64 PIN 44, and demo board maps to D10 header PIN 20
SDA1 = TQFP-64 PIN 43, and demo board maps to D9 header PIN 21
Ground is on header pin 33 and 34
*/
#use i2c(MASTER, SCL=PIN_D10, SDA=PIN_D9, SLOW, FORCE_HW, STREAM=I2CM1) 

/*
Use the LCD - Define the connections on the hardware
*/
#define LCD_ENABLE_PIN  PIN_D0                                    
#define LCD_RS_PIN      PIN_D1                                    
#define LCD_RW_PIN      PIN_D2                                    
#define LCD_DATA4       PIN_E6                                    
#define LCD_DATA5       PIN_E7                                  
#define LCD_DATA6       PIN_D6                                    
#define LCD_DATA7       PIN_D7                                    
#include <lcd.c>
#define LP55321_EN      PIN_B13
#define LP55321_I2C_WADDR    0x64        //Write
#define LP55321_I2C_RADDR    0x65        //Read

//32 entries program
static const unsigned long program[] = {
    0x9c10,        //0 map start
    0x9c9f,        //1 map end
    0x66ff,        //2 ramp up
    0x0200,        //3 wait
    0x07ff,        //4 ramp down
    0x9d80, // 5 map next
    0xa002, // 6 loop to 2
    0x000a, // 7 - empty placeholder
    0x0005, // 8 - empty placeholder
    0x000a, // 9 - empty placeholder
    0x0005, // a - empty placeholder
    0x000a, // b - empty placeholder
    0x0005, // c - empty placeholder
    0x000a, // d - empty placeholder
    0x0005, // e - empty placeholder
    0x000a, // f - empty placeholder
    0x0001, // 10 map begin - start of 2nd page
    0x0002, // 11
    0x0040, // 12
    0x0004, // 13
    0x0008, // 14
    0x0080, // 15
    0x0010, // 16
    0x0020, // 17
    0x0100, // 18
    0x0020, // 19
    0x0010, // 1a
    0x0080, // 1b
    0x0008, // 1c
    0x0004, // 1d
    0x0040, // 1e
    0x0002, // 1f  map end
};

// register stuff
static const unsigned char REG_CNTRL1 = 0x00;
static const unsigned char REG_CNTRL2 = 0x01;
static const unsigned char REG_RATIO_MSB = 0x02;
static const unsigned char REG_RATIO_LSB = 0x03;
static const unsigned char REG_OUTPUT_ONOFF_MSB = 0x04;
static const unsigned char REG_OUTPUT_ONOFF_LSB = 0x05;

// Per LED control channels - fader channel assig, log dimming enable, temperature compensation
static const unsigned char REG_D1_CTRL = 0x06;
static const unsigned char REG_D2_CTRL = 0x07;
static const unsigned char REG_D3_CTRL = 0x08;
static const unsigned char REG_D4_CTRL = 0x09;
static const unsigned char REG_D5_CTRL = 0x0a;
static const unsigned char REG_D6_CTRL = 0x0b;
static const unsigned char REG_D7_CTRL = 0x0c;
static const unsigned char REG_D8_CTRL = 0x0d;
static const unsigned char REG_D9_CTRL = 0x0e;

// Direct PWM control registers
static const unsigned char REG_D1_PWM  = 0x16;
static const unsigned char REG_D2_PWM  = 0x17;
static const unsigned char REG_D3_PWM  = 0x18;
static const unsigned char REG_D4_PWM  = 0x19;
static const unsigned char REG_D5_PWM  = 0x1a;
static const unsigned char REG_D6_PWM  = 0x1b;
static const unsigned char REG_D7_PWM  = 0x1c;
static const unsigned char REG_D8_PWM  = 0x1d;
static const unsigned char REG_D9_PWM  = 0x1e;

// Drive current registers
static const unsigned char REG_D1_I_CTL = 0x26;
static const unsigned char REG_D2_I_CTL  = 0x27;
static const unsigned char REG_D3_I_CTL  = 0x28;
static const unsigned char REG_D4_I_CTL  = 0x29;
static const unsigned char REG_D5_I_CTL  = 0x2a;
static const unsigned char REG_D6_I_CTL  = 0x2b;
static const unsigned char REG_D7_I_CTL  = 0x2c;
static const unsigned char REG_D8_I_CTL  = 0x2d;
static const unsigned char REG_D9_I_CTL  = 0x2e;

static const unsigned char REG_MISC     = 0x36;
static const unsigned char REG_PC1 = 0x37;
static const unsigned char REG_PC2 = 0x38;
static const unsigned char REG_PC3 = 0x39;
static const unsigned char REG_STATUS_IRQ = 0x3A;
static const unsigned char REG_RESET      = 0x3D;

static const unsigned char REG_PROG1_START = 0x4C;
static const unsigned char REG_PROG2_START = 0x4D;
static const unsigned char REG_PROG3_START = 0x4E;
static const unsigned char REG_PROG_PAGE_SEL = 0x4f;

// Memory is more confusing - there are 4 pages, sel by addr 4f
static const unsigned char REG_PROG_MEM_BASE = 0x50;
//static const unsigned char REG_PROG_MEM_SIZE = 0x;//
static const unsigned char REG_PROG_MEM_END  = 0x6f;

static const unsigned char REG_ENG1_MAP_MSB = 0x70;
static const unsigned char REG_ENG1_MAP_LSB = 0x71;
static const unsigned char REG_ENG2_MAP_MSB = 0x72;
static const unsigned char REG_ENG2_MAP_LSB = 0x73;
static const unsigned char REG_ENG3_MAP_MSB = 0x74;
static const unsigned char REG_ENG3_MAP_LSB = 0x75;



void main(void)
{
   char c;
   unsigned int8 delay=0;
   unsigned char val = 0;
   unsigned char i = 0;
   
   LED_ON(GREEN_LED);
//!   LED_OFF(YELLOW_LED);
//!   LED_OFF(RED_LED);
//!   
//!   setup_adc(ADC_CLOCK_INTERNAL | ADC_TAD_MUL_2);
//!   setup_adc_ports(MY_ANALOG_PORTS);
//!   set_adc_channel(AN_POT);
   
   usb_init();
   
   lcd_init();
   delay_ms(1000);
   //printf(lcd_putc,"\a");
   printf(lcd_putc,"\aReady...");
   
   while (TRUE)
   {
      if (usb_enumerated () )
      {
         delay_ms(1000);
         LED_ON(YELLOW_LED);

         If (usb_cdc_kbhit () )
         {
            c = usb_cdc_getc();

            switch(c)
            {
                case 'i':                       //Initialize the led driver
                case 'I':
                {
                    printf(usb_cdc_putc,"In Init\r\n");
                    printf(lcd_putc,"\a");
                    
                    output_low(LP55321_EN);
                    LED_OFF(RED_LED);
                    printf(lcd_putc,"INIT: EN = 0\n");
                    
                    delay_ms(500);
                    
                    output_high(LP55321_EN);
                    LED_ON(RED_LED);
                    printf(lcd_putc,"INIT: EN = 1");
                    
                    //writeReg(0x00 , 0x40);
                    i2c_start(I2CM1);                               //(S) Start Condition
                    i2c_write(I2CM1,LP55321_I2C_WADDR);             //(W) Write the Slave Address
                    i2c_write(I2CM1,REG_CNTRL1);                    //Send Command for REG D8 RED
                    i2c_write(I2CM1,0x00);                          //Logarithmic dimming control for D8 output
                    i2c_stop(I2CM1);    
                    
                    //writeReg(0x36 , 0x53);
                    i2c_start(I2CM1);                               //(S) Start Condition
                    i2c_write(I2CM1,LP55321_I2C_WADDR);             //(W) Write the Slave Address
                    i2c_write(I2CM1,REG_MISC);                    //Send Command for REG D8 RED
                    i2c_write(I2CM1,0x53);                          //Logarithmic dimming control for D8 output
                    i2c_stop(I2CM1);    
        
                    //Set drive current 
                    for(i = 0; i < 9; i++)
                    {
                        //writeReg(0x0n, value); set current
                        i2c_start(I2CM1);                               //(S) Start Condition
                        i2c_write(I2CM1,LP55321_I2C_WADDR);             //(W) Write the Slave Address
                        i2c_write(I2CM1,(REG_D1_I_CTL+i));               //Send Command for REG D8 RED
                        i2c_write(I2CM1,0xAF);                          //Logarithmic dimming control for D8 output
                        i2c_stop(I2CM1);                                 //(P) Stop Condition
                        
                        //writeReg(0x1n, value); set PWM
                        i2c_start(I2CM1);                               //(S) Start Condition
                        i2c_write(I2CM1,LP55321_I2C_WADDR);             //(W) Write the Slave Address
                        i2c_write(I2CM1,(REG_D1_PWM +i));               //PWM val
                        i2c_write(I2CM1,0xFF);                          //Logarithmic dimming control for D8 output
                        i2c_stop(I2CM1);                                 //(P) Stop Condition
                                                     
                    }
                        //Presumably this is to control the ON/OFF for the
                        //driver output... I am turning 0-8 D1-D8 ON
                        i2c_start(I2CM1);                               //(S) Start Condition
                        i2c_write(I2CM1,LP55321_I2C_WADDR);             //(W) Write the Slave Address
                        i2c_write(I2CM1,REG_OUTPUT_ONOFF_LSB);          //Set to log brightness
                        i2c_write(I2CM1,0xFF);                          //
                        i2c_stop(I2CM1); 
                        
                        //Turning ON the last BIT ON D9
                        i2c_start(I2CM1);                               //(S) Start Condition
                        i2c_write(I2CM1,LP55321_I2C_WADDR);             //(W) Write the Slave Address
                        i2c_write(I2CM1,REG_OUTPUT_ONOFF_MSB);          //Set to log brightness
                        i2c_write(I2CM1,0x01);                          //
                        i2c_stop(I2CM1);                                //(P) Stop Condition
                        
   
                    break;
                }
                
                case 'a':                       //Start LED
                case 'A':
                {
                    
                    break;
                }
                
                case 'f':
                case 'F':
                {
                    break;
                }
                
                default:
                {
                
                }
            }
            
         }
//!         delay_ms(1000);
//!         output_high(LP55321_EN);
//!         LED_ON(RED_LED);
//!         delay_ms(1000);
//!         output_low(LP55321_EN);
//!         LED_OFF(RED_LED);
      }
   }
}

CHIP LAYOUT ON CUSTOM BOARD

Not all layers are turned on, the ground planes, etc..  Only top layer (purple), bottom layer (RED)  The charge pump caps are in the opposite layer through vias.  Is this an issue?  Vias can handle up to 1Amp.  I imagine the switching frequency is less than 20MHz.

Hi Roberto,

Your schematic and layout is OK. And it is also no problem to ground the TRIG pin and float the INT pin.

Maybe there are some issues with power up sequence. Could you help to check your code is following as below? To light up the LED, CHIP_EN bit should be written high and EN pin should be turn high.

The Start-up delay is 500 μs. Then set charge pump mode to 1x or 1.5x.

After that, turn on the LED channel you want.

Finally adjust the PWM and current bit to light up the LED.

Dear Hardy,

I will try that and get back to you.  It is possible that all these addresses are not receiving the correct value.

So here is what I plan to sequence

Register -> Value

0x00 -> 0x40 (0100 0000) LP55321 Enabled

0x36 -> 0x18 -> for automatic control  I guess I will try 0x08 (for to bypass mode), 0x10 (x1.5 mode), and 0x18 for automatic mode

0x05 -> 0xFF ->  I want them all ON D1 - D8

0x04 -> 0x01-> D9

I will post back to if the results are positive.

I tried all that and didn't work.  I suspect the chips are bad.  What could cause them to be bad?

RR

Hi Roberto,

Can you read these registers after you write in?

Do you have our EVM board? To confirm whether the chip is damaged, you could de-mount it from your board and solder it to EVM to test the function.

I do not have the demo board, but I have been focused on writing to the registers. I will try reading all the registers and see if I can.  What are the defaults so I can compare?

Regards,

RR

The datasheet shows table 3 with defaults but somebits are don't care. I suppose i will mask the don't care bits and compare.

Dear Hardy,

I read the register and initially they read  0xFF, then I write only the register you highlighted, then I read back and the LED turn ON.  For some reason, if I don't read them first, writing to them won't work.  So I have to read them, then write them.

For example I was turning on the RED.  Then I changed the code to turn on the Green.  The change won't take effect until I read all register, then write them.  This is bizzare why this is.  I was thinking the I2C bus capacitance was higher, and maybe the reading process charges the I2C lines, then writing them works.  So I changed the pull-ups from 4.99k to 2.47k and still the same thing.  It is not the pull-ups.  I put the scope the signals look good with a fast rising edge in both pull-up values.

Why do I need to read them all and write them to make it work is a mystery.  I can't figure that out..

READING REGISTERS....
0 -> LP55231_REG_00 = 0x40
1 -> LP55231_REG_01 = 0x00
2 -> LP55231_REG_02 = 0x00
3 -> LP55231_REG_03 = 0x00
4 -> LP55231_REG_04 = 0x01
5 -> LP55231_REG_05 = 0xFF
6 -> LP55231_REG_06 = 0x00
7 -> LP55231_REG_07 = 0x00
8 -> LP55231_REG_08 = 0x00
9 -> LP55231_REG_09 = 0x00
10 -> LP55231_REG_0A = 0x00
11 -> LP55231_REG_0B = 0x00
12 -> LP55231_REG_0C = 0x00
13 -> LP55231_REG_0D = 0x00
14 -> LP55231_REG_0E = 0x00
16 -> LP55231_REG_10 = 0x00
17 -> LP55231_REG_11 = 0x00
18 -> LP55231_REG_12 = 0x00
19 -> LP55231_REG_13 = 0x00
20 -> LP55231_REG_14 = 0x00
21 -> LP55231_REG_15 = 0x00
22 -> LP55231_REG_16 = 0x00
23 -> LP55231_REG_17 = 0x00
24 -> LP55231_REG_18 = 0x20
25 -> LP55231_REG_19 = 0x00
26 -> LP55231_REG_1A = 0x00
27 -> LP55231_REG_1B = 0x00
28 -> LP55231_REG_1C = 0x00
29 -> LP55231_REG_1D = 0x00
30 -> LP55231_REG_1E = 0x00
26 -> LP55231_REG_1A = 0x00
27 -> LP55231_REG_1B = 0x00
28 -> LP55231_REG_1C = 0x00
29 -> LP55231_REG_1D = 0x00
30 -> LP55231_REG_1E = 0x00
31 -> LP55231_REG_1F = 0x00
32 -> LP55231_REG_20 = 0x00
33 -> LP55231_REG_21 = 0x00
34 -> LP55231_REG_22 = 0x00
35 -> LP55231_REG_23 = 0x00
36 -> LP55231_REG_24 = 0x00
37 -> LP55231_REG_25 = 0x00
38 -> LP55231_REG_26 = 0xAF
39 -> LP55231_REG_27 = 0xAF
40 -> LP55231_REG_28 = 0xAF
41 -> LP55231_REG_29 = 0xAF
42 -> LP55231_REG_2A = 0xAF
43 -> LP55231_REG_2B = 0xAF
44 -> LP55231_REG_2C = 0xAF
45 -> LP55231_REG_2D = 0xAF
46 -> LP55231_REG_2E = 0xAF
36 -> LP55231_REG_24 = 0x00
37 -> LP55231_REG_25 = 0x00
38 -> LP55231_REG_26 = 0xAF
39 -> LP55231_REG_27 = 0xAF
40 -> LP55231_REG_28 = 0xAF
41 -> LP55231_REG_29 = 0xAF
42 -> LP55231_REG_2A = 0xAF
43 -> LP55231_REG_2B = 0xAF
44 -> LP55231_REG_2C = 0xAF
45 -> LP55231_REG_2D = 0xAF
46 -> LP55231_REG_2E = 0xAF
47 -> LP55231_REG_2F = 0x00
48 -> LP55231_REG_30 = 0x00
49 -> LP55231_REG_31 = 0x00
50 -> LP55231_REG_32 = 0x00
51 -> LP55231_REG_33 = 0x00
52 -> LP55231_REG_34 = 0x00
53 -> LP55231_REG_35 = 0x00
54 -> LP55231_REG_36 = 0x10
55 -> LP55231_REG_37 = 0x00
56 -> LP55231_REG_38 = 0x00
57 -> LP55231_REG_39 = 0x00
58 -> LP55231_REG_3A = 0x48
59 -> LP55231_REG_3B = 0x00
60 -> LP55231_REG_3C = 0x00
61 -> LP55231_REG_3D = 0x00
62 -> LP55231_REG_3E = 0x00
63 -> LP55231_REG_3F = 0x19
64 -> LP55231_REG_40 = 0x00
65 -> LP55231_REG_41 = 0x00
66 -> LP55231_REG_42 = 0x00
67 -> LP55231_REG_43 = 0x03
68 -> LP55231_REG_44 = 0x48
69 -> LP55231_REG_45 = 0x00
70 -> LP55231_REG_46 = 0x00
71 -> LP55231_REG_47 = 0x00
72 -> LP55231_REG_48 = 0x00
73 -> LP55231_REG_49 = 0x00
74 -> LP55231_REG_4A = 0x00
75 -> LP55231_REG_4B = 0x00
76 -> LP55231_REG_4C = 0x00
77 -> LP55231_REG_4D = 0x10
78 -> LP55231_REG_4E = 0x20
79 -> LP55231_REG_4F = 0x00
80 -> LP55231_REG_50 = 0x00
81 -> LP55231_REG_51 = 0x00
82 -> LP55231_REG_52 = 0x00
83 -> LP55231_REG_53 = 0x00
84 -> LP55231_REG_54 = 0x00
85 -> LP55231_REG_55 = 0x00
86 -> LP55231_REG_56 = 0x00
87 -> LP55231_REG_57 = 0x00
88 -> LP55231_REG_58 = 0x00
89 -> LP55231_REG_59 = 0x00
90 -> LP55231_REG_5A = 0x00
91 -> LP55231_REG_5B = 0x00
92 -> LP55231_REG_5C = 0x00
93 -> LP55231_REG_5D = 0x00
94 -> LP55231_REG_5E = 0x00
95 -> LP55231_REG_5F = 0x00
96 -> LP55231_REG_60 = 0x00
97 -> LP55231_REG_61 = 0x00
98 -> LP55231_REG_62 = 0x00
99 -> LP55231_REG_63 = 0x00
100 -> LP55231_REG_64 = 0x00
101 -> LP55231_REG_65 = 0x00
102 -> LP55231_REG_66 = 0x00
103 -> LP55231_REG_67 = 0x00
104 -> LP55231_REG_68 = 0x00
105 -> LP55231_REG_69 = 0x00
106 -> LP55231_REG_6A = 0x00
107 -> LP55231_REG_6B = 0x00
108 -> LP55231_REG_6C = 0x00
109 -> LP55231_REG_6D = 0x00
110 -> LP55231_REG_6E = 0x00
111 -> LP55231_REG_6F = 0x00
112 -> LP55231_REG_70 = 0x00
113 -> LP55231_REG_71 = 0x00
114 -> LP55231_REG_72 = 0x00
115 -> LP55231_REG_73 = 0x00
116 -> LP55231_REG_74 = 0x00
117 -> LP55231_REG_75 = 0x00
118 -> LP55231_REG_76 = 0x00

READ ALL REGISTERS COMPLETED...
ENABLE CHIP FIRST...
REG_CTRL1 = 0x40
REG_RESET = 0xFF
Chip Intialized...

Hi David,

Sorry for late reply. Normally the device should have response action Immediately after you write command in it. Can you help to capture the plot of SDA and SCL when you write a command to device to see if it have normal acknowledge signal back? Also capture the write signal after you read all to compare if they have any difference.