The operation of TLC5955

Hamrouni Amira

Prodigy 90 points

Other Parts Discussed in Thread: TLC5955

Hello,

I work on the control of a TLC5955 by a microcontroller. But I could not.

LAT = 0,
I send values for eatch output (768 bit) send data by sin , clocked witch sclk

Data={DC=MC=BC=max , DSPRPT=0, TMGRST=0; REFRESH=0;ESPWM=0,LSDVLT=0, bit[760..767]=[01101001], MSB=1}

LAT = 1,
Delay(1ns)
I send values for eatch output (768 bit and MSB=0) send data by sin , clocked witch sclk
For ( c=0; c<65535;c++) GBclk=1; delay=.1; GBclk=0; delay=.1;
In loop to point 1

the LEDs turn off

over 8 years ago

0 Hamrouni Amira over 8 years ago

Prodigy 90 points

I read the datasheet 3 times but it is not clear, how to have a good functioning of tlc5955. Can you correct me the steps described above ? thank you.

0 Feifei Shen over 8 years ago in reply to Hamrouni Amira

TI__Expert 3275 points

Hi Amira,

For tlc5955, you can send the sequence below:

1. Send control data (769bit) , [suggest DC=MC=BC=max , DSPRPT=1, TMGRST=1; REFRESH=1; ESPWM=0]

2. Latch 0

3. Latch 1

4. Latch 0

5. Send Grayscale data (769bit) ,

6. Latch 0

7. Latch 1

8. Latch 0

9. GSCLK free run.

Best regards,

Feifei

0 Hamrouni Amira over 8 years ago in reply to Feifei Shen

Prodigy 90 points

Hi Feifei Shen,

Thanks for your prompt response!

Yes, i do the same steps but nothing out for my pine. i supply my TLC5955 for 3.3V voltage.

0 Feifei Shen over 8 years ago in reply to Hamrouni Amira

TI__Expert 3275 points

Hi Amira,

Pls check below other than timing.

1. The PowerPad must be connected to GND layer. They are power GND for the device. You could check it on datasheet 41.

Best regards,

Feifei

0 Hamrouni Amira over 8 years ago in reply to Feifei Shen

Prodigy 90 points

Hi Feifei,

I have checked my PowerPad and he is connected to GND layer. The LEDs turn off

Best Regards,
Amira

0 Hamrouni Amira over 8 years ago in reply to Hamrouni Amira

Prodigy 90 points

Hi Feifei,

do you have another proposal ?

Best Regards,
Amira

0 Feifei Shen over 8 years ago in reply to Hamrouni Amira

TI__Expert 3275 points

Hi Amira,

What's the Vcc voltage you are using for tlc5955 and SCLK/SIN/LAT signal high level voltage?

I am asking because this device is CMOS level interface.

Best regards,

Feifei

0 Hamrouni Amira over 8 years ago in reply to Feifei Shen

Prodigy 90 points

Hi Feifei,

I apply:
Vcc=3.3V
SCLK=3.3V
SIN=3.3V
LAT=3.3V

because datasheet page 7 say:
Vcc=[3V .. 5.5V]
Vih for SIN, SCLK ,LAT, GSCLK = [0.7*Vcc .. Vcc]

Best Regards,
Amira

0 Feifei Shen over 8 years ago in reply to Hamrouni Amira

TI__Expert 3275 points

Hi Amira,

From your waveform, seems SCLK signal is abnormal(high voltage level), pls check.

The signal high level should be 3.3V as you described.

Best regards,

Feifei

0 Hamrouni Amira over 8 years ago in reply to Feifei Shen

Prodigy 90 points

Hi Feifei,

This is my oscilloscope kidding, SCLK signal is 3.3V.

To send data I do not use SPI. Just I sent bit SIN following SCLK. The program to other TLC using SPI. Is that the use SPI of the impact on the transmission of the program ?

Best Regards,
Amira

0 Feifei Shen over 8 years ago in reply to Hamrouni Amira

TI__Expert 3275 points

Hi Amira,

Could you using oscillator monitor SCLK/SIN/LAT/GSCLK?

We can checking your signal.

Best regards,

Feifei

0 Hamrouni Amira over 8 years ago in reply to Feifei Shen

Prodigy 90 points

Hi Feifei Shen,

Best regards,

Amira

0 Feifei Shen over 8 years ago in reply to Hamrouni Amira

TI__Expert 3275 points

Hi Amira,

Can you explain your first waveform?

What are you sending? I see 8 LAT signal in the waveform. How many pcs of tlc5955 are you cascaded?

Best regards,

Feifei

0 Hamrouni Amira over 8 years ago in reply to Feifei Shen

Prodigy 90 points

Hi Feifei,

Init Default Data :

I sind 769 bit all zeros except: bit_760=0 ; bit_761=1 ; bit_762=1 ; bit_763=0 ; bit_764=1 ; bit_765=0 ; bit_766=0; bit_767=1; and MSB_bit_768=1;
I written twice

Init Data DC BC FC:

I sind 769 bit all zeros except:
Bit_DC[0..335]=1;
Bit_MC[336..344]=101;
Bit_BC[345..365]=1;
Bit_DSPRPt=1
Bit_TMGRST=1
Bit_REFRESH=1
bit_760=0 ; bit_761=1 ; bit_762=1 ; bit_763=0 ; bit_764=1 ; bit_765=0 ; bit_766=0; bit_767=1; and MSB_bit_768=1;
I written twice

GS Data 8000h for 1 outxn:

I sind 769 bit
For 1 outxn, I sind 8000h
MSB_bit_768=0;

My first waveform:

I synced my data SIN with the SCLK. When I finished sending the data series of the MSB to LSB. I sent a rising edge for LAT.

I have 8 LAT because:

I written twice “Init Default Data” see page 21 for Datasheet TLC5955
I written twice “Init Data DC BC FC”
I constantly sends data “GS Data 800h for 1 outxn”

I have one TLC5955

Best regards,

Amira

0 Feifei Shen over 8 years ago in reply to Hamrouni Amira

TI__Expert 3275 points

Hi Amira,

Actually you don't need send "Init Default Data" twice.
Only twice"Init Data DC BC FC" is enough.

Also, not sure why you are keep constantly send GS data.
Just one time is OK unless you want to update the new data.

From your 2nd waveform(test time: 16:07), seems you are not sending
bit_760=0 ; bit_761=1 ; bit_762=1 ; bit_763=0 ; bit_764=1 ; bit_765=0 ; bit_766=0; bit_767=1; and MSB_bit_768=1

You are sending
bit_760=1 ; bit_761=1 ; bit_762=0 ; bit_763=1 ; bit_764=0 ; bit_765=0 ; bit_766=1; bit_767=1; and MSB_bit_768=0

Pls check.

Best regards,
Feifei

0 Jonathon Ross over 8 years ago in reply to Feifei Shen

Prodigy 10 points

I've been trying to warp my head around the operation of this part, but I'm having a hard time determining what exactly I'm supposed to be doing.

I'd like to simply use GSDATA to configure how bright the LEDs are. But it appears that I need to us GSCLK to get the driver to turn on.

It seems that if I send the 769 bit configuration data (twice to allow MC data to be configured) and the follow it by an array of all 0xFF except for the first (bit 768) cleared, that it should turn all the LEDs on to full brightness.

Is GSCLK required to be able to do this? Should I write 65535 clock cycles to GSCLK before the latch?

Any help would be much appreciated.

0 Feifei Shen over 8 years ago in reply to Jonathon Ross

TI__Expert 3275 points

Hi Ross,
Yes, GSCLK is required.
If you just want to bright the LEDs.
The easiest sequence is
1. Twice configure data.(including latch)
2. GSData array.(including latch)
3. 1 GSCLK.

The LED will be light, not sure this is what you want.

Best regards,
Feifei

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The operation of TLC5955