Front I/O

Version 3.3 by Kevin Wiki on 2024/07/04 23:07

Pinout

There is a single cable that controls four parts, each half side of I/O LED and center column of blue LEDs.

xserve io main cable pinout.drawio.png

How we got here

Measure out the ground and power signals by comparing with other chips on board. E.g. we find [SAA1064T] datasheet, locate the GND (Vee) and 5V (Vcc) and measure connectivity (0 ohm resistance) between chip pins and cable pins. This gives us pins GND 2 & 8 and PWR 16 & 22.

We keep doing this for SCL & SDA pins on SAA1064T chip and find pins 14 & 15 and 20 & 21 are I2C clock and data pins for each chip.

Finding i2c chip address

SAA1064T

Reading the datasheet for SAA1064T chip we find that: "This results in the corresponding valid addresses HEX 70, 72, 74 and 76 for writing and 71, 73, 75 and 77 for reading. All other addresses cannot be acknowledged by the circuit". Giving us a clue what we are looking for, i2c addresses 0x70, 0x72 or 0x74.

PCA9554

asdf

Code example finding i2c addresses

We can test the following addresses manually or use the following code snippet:

/*I2C_scanner
  This sketch tests standard 7-bit addresses.
  Devices with higher bit address might not be seen properly.*/

#include <Wire.h>

void setup() {
  Wire.begin();

  Serial.begin(9600);
while (!Serial);
  Serial.println("\nI2C Scanner");
}

void loop() {
  byte error, address;
int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
for (address = 1; address < 127; address++ ) {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

   if (error == 0) {
      Serial.print("I2C device found at address 0x");
     if (address < 16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println(" !");

      nDevices++;
    }
   else if (error == 4) {
      Serial.print("Unknown error at address 0x");
     if (address < 16)
        Serial.print("0");
      Serial.println(address, HEX);
    }
  }
if (nDevices == 0)
    Serial.println("No I2C devices found\n");
else
    Serial.println("done\n");

  delay(5000);
}

i2c multiplexing with TCA9548

We have two sets of chips, one for left and one for right where we have two different i2c chips on each side for controlling lights. Since the chips controlling their respective parts have the same address for each side, we can't distinguish them from each other. To handle this we use a i2c multiplexer to selectively communicate with one half at a time, switching TCA9548 between two different output ports.

Code example finding i2c ports

To verify wiring, connection, output ports and device addresses run the following script:

/**
* TCA9548 I2CScanner.ino -- I2C bus scanner for Arduino
*
* Based on https://playground.arduino.cc/Main/I2cScanner/
*
*/

#include "Wire.h"

#define TCAADDR 0x70

void tcaselect(uint8_t i) {
if (i > 7) return;

  Wire.beginTransmission(TCAADDR);
  Wire.write(1 << i);
  Wire.endTransmission();
}

// standard Arduino setup()
void setup()
{
   while (!Serial);
    delay(1000);

    Wire.begin();

    Serial.begin(9600);
    Serial.println("\nTCAScanner ready!");

   for (uint8_t t=0; t<8; t++) {
      tcaselect(t);
      Serial.print("TCA Port #"); Serial.println(t);

     for (uint8_t addr = 0; addr<=127; addr++) {
       if (addr == TCAADDR) continue;

        Wire.beginTransmission(addr);
       if (!Wire.endTransmission()) {
          Serial.print("Found I2C 0x"); Serial.println(addr,HEX);
        }
      }
    }
    Serial.println("\ndone");
}

void loop()
{
}

SAA1064T data for driving center IO LED stack

Center IO stack is a stack of 23 LED's, 22 blue and 1 green for ethernet activity. These are duplicated next to each other and driven by each their SAA1064T chips. Earlier we found the i2c address and just by playing around figured out that 4 segments of 1 byte binary values are used to set ship register.

void fillColumns() {
  Serial.println("filling columns");
  Wire.beginTransmission(saa1064);
  Wire.write(1);
  Wire.write(0x7F);   // 127 - 1111111
Wire.write(0x7F);   // 127 - 1111111
Wire.write(0x7F);   // 127 - 1111111
Wire.write(0x1F);   // 31 - 11111
Wire.endTransmission();

  colsFilled = 1;
}

Here the last byte we send only is 5 bits since we only have 5 LEDs instead of 6 to address (total of 23). Also note that we start the transmission with a single bit.

Pinouts voltages from MLB

Powered off:

PWR fail LED - 0.00 V
UID LED - 4.5V
OH/Fan fail LED - 4.72 V
NIC1 LED - 0.8 - 2.6 V
NIC2 LED - 2.95 V
UID SW - 2.8V
HDD LED - 0.00 V
Power LED P3V3 - 0.00V
Power LED - 0.00 V after unplug grows

Powered on:

PWR tail LED - 3.47 V
UID LED - 4.85V
OH/Fan failed LED - 5 V
NIC 1 LED - 1.2 - 2.9 V
NIC 2 LED - 3.2 V
UID SW - 3V
HDD LED - 3 V
Power LED P3V3 - 3.30V
Power LED - 0.87 V

Contents

Pinout
How we got here

Figure 1: Sea

Figure 2: Waves