Uniquely identify a PCB through an external ROM

Question

Dear all, 
 
 I need to uniquely identify a PCB that uses ADUCM3029 as micro-controller. For that i'm connecting a ROM using 1-wire protocol in a GPIO pin. I browsed the ADI drivers and examples however I didn't find anything related to this matter, so I started writing a 1-wire protocol driver to read this ROM. One of the configuration needed is a pull-up resistor connecting to this pin. I'm asking: 
 what is value of the internal GPIO pull-up resistors? 
 Did Analog Devices has already an example or documentation concerning the 1-wire protocol? 
 
 Regards, 
 Mohamed Amine MESSAOUD

ADIApproved · Accepted Answer

Hello! 
 I was able to find two potential problems: 
 1. Configuring SysTick to interrupt every 1us could hang the program because the interrupt would be too often for it to do much else. Try to make #define TICKS (26000000u/100000u) and adjust the STANDARD_SPEED defines accordingly considering that now the timer ticks every 10us instead of every 1us. 
 2. You should enable the input driver for the GPIO pin you are using by calling adi_gpio_InputEnable. 
 Regards, 
 Andrei.)

ADIApproved · Answer

I think the 1us time delay is only required for overdrive mode. I believe that it can work with 10us delay. 
 This tutorial on 1-wire mentions the time intervals that can be used in 1-wire implementation. 
 https://www.maximintegrated.com/en/products/1-wire/flash/overview/index.cfm 
 You can change: 
 STANDARD_SPEED_A 1 
 STANDARD_SPEED_B 7 (or 8 if the slave is particularly slow) 
 STANDARD_SPEED_E 1 (or 0 if the slave is particularly fast) 
 STANDARD_SPEED_F 5 (or 6 if STANDARD_SPEED_E is 0) 
 And the rest are evenly divided by 10. 
 The critical part is the STANDARD_SPEED_E because in the tutorial the master needs to read at exactly 15us. If it does not work with 1 or 0 try changing #define TICKS (26000000u/200000u) and use 
 STANDARD_SPEED_A 2 
 STANDARD_SPEED_B 12 
 STANDARD_SPEED_E 1 
 and the rest are divided by 5. 
 Hope this helps. 
 All the best, 
 Andrei

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Uniquely identify a PCB through an external ROM