[Electronics] nRF51822 Bring up notes

1. nRF51 SDK is different than nRF5. Only nRF51 SDK works. Highest version is 10.0.0 at this time if SoftDevice is needed.

2. S110 is the best SD to use for BLE peripheral. S120 is for BLE center or peripheral. S130 is for BLE center and peripheral.

3. Certain SDK can only use certain SoftDevice. Use the table below to check
   Compatibility matrix for nRF51:
   https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcomp_matrix_nrf51%2FCOMP%2Fnrf51%2Fnrf51_comp_matrix.html

4. Application address is following after SoftDevice. Different SoftDevice version has different sizes. So for different SOftDevice, the start address of Application and usable space is different.
   SoftDevice 5.x.x and 6.x.x:
   
   SoftDevice 7.x.x:
   
   SoftDevice 8.x.x:
   
   SoftDevice 9.x.x:
   
   Note that the IRAM size depends on your chip revision. Go to the compatibility matrix to see which chip version you have. It exists two sizes, 16kB and 32kB. IRAM start and size should add up to 0x4000 for 16kB or 0x8000 for the 32kB version.
   P.S nRF51 sDual bank flash layout
   http://194.19.86.155/nRF5_SDK/nRF51_SDK_v6.x.x/doc/6.0.0/s110/html/a00089.html

5. Error "Cannot Write to RAM for Flash Algorithms"
   Make sure J-Link setting for RAM Algorithm is correct, same as your IRAM size.

6. Keil 4.0 projects needed to upgrade to Keil 5 before being compiled. Project - Manage - "Migrate to Version 5 Format".

7. Any GPIO can be used for UART.

8. Minicom in Linux is much better than any UART debug software under Windows platform.

9. I have difficulty to debug/download project(hex) using ST-Link V2. Keil can find debugger with no problem. but not be able to find DUT. To be check.

10. ST-Link works with Arduino IDE + nRF51822 with no problem.