Quick Reference of nRF51822

Created: Jul, 2015

Last modified: Aug, 2015

Here are links to posts or tutorials I found useful when learning nRF51822.

• ARM mbed talks about firmware over the air (FOTA) update

• Why do I get “Error: Flash download failed – Cortex-M0” when downloading a project from Keil? This and [this] (https://devzone.nordicsemi.com/question/15208/error-flash-download-failed-cortex-m0/)

• Keil v5 doesn’t recognize nRF51822 devices

• Sample ADC in nRF51 with SoftDevice

• nRF51 development with Eclipse and GCC: Nordic blog post,
  RedBearLab

• Yunjia nRF51288 pinout

• Dynamic temperature info advertizing

• Power and clock model of peripherals in nRF51822

• Low-frequency clocks in nRF51822

• ADC input impedance in nRF51822

• ADC conversion time is about 68 us in nRF51822, which makes the max sample rate about 14 kHz; see here.

• How to configure high-drive on the GPIO pins of nRF51822.

• How to deal with the unused GPIO pins on nRF51822

• When using app_button libraries:

  • The app_buttons libraries use an application timer (sourced by RTC) and two timer events implicitly. One may need to check the max allowed timers and size of timer queue to accommodate.
  • GPIO input may have internal pull-up or pull-down resistor. This may give weird behavior if not taken into consideration. To disable it and use external pull-up or pull-down, do something like (nRF51 SDK 8.0.0)

static app_button_cfg_t buttons[] =
{
	// this enables internal pull-up
    // {BUTTON_SS, false, BUTTON_PULL, button_event_handler}  

    // this disables the internal pull-up, to use the external pull-up
    {BUTTON_SS, APP_BUTTON_ACTIVE_LOW, NRF_GPIO_PIN_NOPULL, button_event_handler}  
};

• Flash write/erase cycles of nRF51822 is 2000 minimum, according to Table 19 in the Product Specification v 3.1.

• The nRF51822 internal (die) temperature characteristics: results reported by a user in Nordic’s Devzone.

• Interpretation of nRF51822 die temperature.

• Peripheral protection and usage by SoftDevice

• A non-blocking delay in nRF51822 using app timers

• nRF51 current consumption for common scenarios

• Understand the concept of notification: “This operation (notification) is initiated by the server when a new value is written to a notify-enabled characteristic. If the client has subscribed to notifications on that characteristic, then the new value is pushed to the client when it is written. Notifications are not acknowledged, but you may send more than one notification in a single connection interval, which can be helpful for maximizing throughput. Notifications cannot be enabled by the server; they must be enabled by the client in order for the actual data transmission to occur.” from this post.