Guzunty Pi LED driver core troubleshooting notes

Now I am looking more closely the 4 digit LED driving signals.  When I first read the following statement in the demo program.  I thought the master clock is 5MHz.  Actually I think it is 5MHz counted down many times to 1.17KHz x 4 = 4.68KHz.  The further counted down 1.17 KHz is then used to multiplex the 4 LED digits, I think.

gz_clock_ena(GZ_CLK_5MHz, 0xfff); // Turn on the slowest clock we can


Now I am thinking of using HC04 quad open collector NAND gates to level shift the 3V3 signals to 5V0.

I will also use ULN2803 to shift the segment signals from 3V3 to 5V0.

I am thinking of using HC573 to buffer the ULN2803 outputs to drive the LEDs.

One more thing I am not sure is that it appears that the LED driver core needs to power reset often, or for the first time after power reset, otherwise it will not start.  I need to verify this later.



*** 


 * gz_led_demo.c - guzunty
...
gz_clock_ena(GZ_CLK_5MHz, 0xfff); // Turn on the slowest clock we can
...
unsigned char payload[4];
...
gz_spi_set_width(4);              // Pass blocks of 4 bytes on SPI
    while (1) 
    {
      int i = 0;
      {
        time_t t;
        time(&t);
        char time_buf[4];
        char time_str[25];
        sprintf(time_str, "%s",ctime(&t));
        time_buf[0] = time_str[11];
        time_buf[1] = time_str[12];
        time_buf[2] = time_str[14];
        time_buf[3] = time_str[15];

for (; i < 4; i++) 
{
 payload[i] = ~font[(unsigned char)time_buf[i]];
   }

   if (colon != 0) 
{
 payload[1] &= ~0x80;
 colon = 0;
        }
        else 
{
 colon = 1;
   }
 }
 
 ...

 gz_spi_write(payload);          // pass display bytes to SPI
      sleep(1);
 }
    }
...

gz_spi_close();                   // close SPI channel

    ...
gz_clock_dis();                   // turn off GPIO clock



digit_enas<0> 
digit_enas<1> 
digit_enas<2> 
digit_enas<3>

.END