Hardware Build States. What you may or not have fitted on your board.

What you may have.

These boards are supplied in various build states. This means you may not have all the parts (some shown in photos below) that you will need to get the board talking to you.

On the first picture, the important points are:-

1. J7 Serial interface pins and J8 JTAG pins. At least in the early stages of understanding the functions of this board, these pins make control and monitoring of the board easier. The Serial interface is a 3V3 interface. So make sure any USB-Serial module you connect can be set-up for this. The JTAG pins will make it easier to update and monitor the PL side of the Zynq device but it is not actually necessary. the Device can be configured from the boot device.
2. TF or uSD Card slot. Again you can live without this device, but your development life will be easier if you have one.

Less Important

3. Y3 Ethernet Crystal(25.000MHZ). This device is not actually needed. The Ethernet Phy is connected to the PL side of the Zynq. This means the PL logic needs to be programmed for the Ethernet connector to work. The PL can provide the required clock instead of the Crystal.
4. U67 &U68 Opto-isolators(EL817). These devices are not really required unless you specifically want to use them. In this case, if they are missing then they will need to be fitted. :-)

On the underside of the board, the important points are:-

1. D24. Many boards are supplied without this device. This device is not essential as the board can be powered vis the 3 2mm pitch data connectors. However, the J4 Molex connector is preferred as it provides additional filtering and should be an easier connector to source. One of the other large diodes (like D23) can be moved to D24 if the DATA3 is not going to be used to provide power.
2. BOOT Select Resistor: R2577 and R2584. The resistor is on R2584 by default, which indicates boot from NAND. If you want to boot from TF card, move R2584 to R2577.

Less important.

3. U69 &U70 Opto-isolators(PC817). These devices are not really required unless you specifically want to use them. In this case, if they are missing then they will need to be fitted. :-)
   If U69 and U70 are present, then pin 4 (labelled as pwm) of J4/J5 can only be used as outputs. The output side of the opto-isolator is connected the VCC pins on J3/4/5 through pull-up resistors R2550 and R2556, so make sure anything connected to pin 4 can handle the voltage on J3/4/5.

Information about missing components and what different.

Missing: (next to J5, J3 Fan Headers)

U67, R2546, R2544, R2545

U68, R2548, R2549, R2547

U69, R2554, R2551

U70, R2557, R2555

Added:

R2553, R2552, R2554, R2557 33 ohm

33 ohm resisters are bypassing the missing opto-isolators and resistors for PWM and SPEED for fan.

Due to no Isolation be careful if applying more than the maximum allowed 1.2 to 3.3V of FPGA I/O set Voltage. In addition, pin 3 on J3 and J5 (labelled as speed) is connected to 3.3V via pull-up resistors R1344 and R1361, so using logic levels less than 3.3V should probably be avoided on those pins. Alternatively, just remove those resistors.

Missing: (next to U24 Lan)

Y3 25MHz xtal

C377, C380 22pF

No oscillator for U24 LAN

Missing: (next to U72)

C2394 100nF

C2398 3.9uF

not really an issue as U72 IC and other components are missing and these are just extra bypass caps

SWITCH S3 can be added if you short out missing R2649 Zero Ohm Resistor or link. Or you can just link right leg of SW2 to right leg of SW3 if looking from front of PCB. (leg closest to LAN socket)

X5 50MHz 3225 oscillator can be added, you need to add 0 ohm resistor or link at R1372 and L29 on bottom of PCB.

---

TODOs:

From various discussions on the telegram chat, pasting it here so that it doesn't get lost:

• Implementing reset via board supervisor chip

  From time to time I have wished there was a reset button on the board, a member here mentioned that there is a power supervisor chip, i lolled it up and it has an unused ready made reset button input. All that is needed is a button n/o switching to ground. I haven't tried it yet but it looks as if there is just enough room to solder one on the board.

• Add info about RTC

  Also I have an idea what the X3 chip + Y2 crystal might be used for - based on the Y2 footprint which allows cylindrical crystals, it could be a RTC

  X3 connects to A15 & D13, these are I2C, the chip pinout matches DS1307 RTC.

  The fact that the rtc looks to be powered from Vcc will limit its usefulness, it should have a battery.

Update: DS1307 uses 5V supply, the RTC is connected to 3V3 supply. The PCF8523 RTC can use 1V0 to 5V5 supply.

• Add info about Eth PHY and its clocking

  I looked up the ethernet phy: https://cdn.sos.sk/productdata/14/88/0bf34b90/ip101ga.pdf the datasheet says, that the 25Mhz quartz is not needed the clock can be derived from the TXCLK/RXCLK

• Info for people wanting to use the XADC facility.

  I believe that there will be problems if anyone wanted to use the XADC inputs on the Zynq. The details for this are in Xilinx User Guide UG480. The problem is that there is no power connection to the VCCADC pin (J9) on the Zynq. This looks to be a design error or oversight. To allow this to work a clean connection to a 1.8V supply should be connected to C327 on the pin nearest C2350.
  
  In addition, there will be no power to the VREFP pin (L9). This is not required as an internal reference can be used. Alternatively, a 1V25 ref voltage could be supplied to C664 on the pin furthest from the data connectors.