Hardware Reference
In-Depth Information
Finally, the SoftDevice's architecture is nonintrusive to application developers. Because
it runs independently and the application does not need to link against any set of libra‐
ries, both SD and application updates can be performed separately with no dependen‐
cies, much in the way one can update a Linux kernel or user-space libraries independ‐
ently without worrying about the other side being affected by the update.
On the down side, the SoftDevice requires system resources that will not be available
for your own application's use. The S110 SoftDevice allocates the bottom 80 KB of flash
and 8 KB of SRAM, leaving you with 176 KB flash and 8 KB SRAM for your own
application (assuming the 256 KB version of the nRF51822 is being used).
The SoftDevice design also introduces latency and architectural limitations, as higher-
level code needs to make calls down to the SoftDevice from your higher-level code,
which happens through sofware interrupts on the ARM core.
As with any big engineering task, the numerous benefits the SoftDevice brings to the
table require some sacrifices, mainly around timing and hard real-time requirements.
Working with the nRF51822-EK
If you are interested in evaluating the nRF51822, the best platform to begin with is
Nordic's
nRF51822-EK
.
As shown in
Figure 5-1
, this evaluation kit includes two devel‐
opment boards: the PCA10001 (shown on the left) and the PCA10000 (shown on the
right).
Figure 5-1. Nordic Semiconductor's nRF51822-EK
The PCA10000 is a small USB dongle used primarily for debugging, either by simulating
a central device via Nordic's Master Control Panel or as a sniffer to push data out to
Wireshark (both of which are discussed in
Chapter 7
). But it's also a full-featured de‐
velopment board on its own, with an integrated Segger J-Link that allows you to program
and debug the firmware using a variety of development tools.
