Hot skills in Embedded and IoT

Based on my observation in the job market, the following skills are currently in demand in embedded systems surrounding IoT development:

1. 802.11 (WiFi)
2. Bluetooth, especially Bluetooth 4.0 + Low Energy (BLE) or newer
3. Zigbee (IEEE 802.15.4)
4. Z-Wave: Based on ITU G.9959 (PHY) and Z-Wave Application layer
5. Bonjour (mDNS/DNS-SD)
6. SSDP (Simple Service Discovery Protocol)
7. OCF (Open Connectivity Foundation's uPnP Device Control Protocol)
8. TCP/UDP
9. TLS (Transport Layer Security)
10. CoAP (Constrained Application Protocol; RFC-7252)
11. HTTP, especially RESt API
12. MQTT (Mosquitto)
13. MultiThread
14. Websockets
15. RESTful (Representational State Transfer) architecture
16. Rust (Rust is a programming language that’s focused on safety, speed, and concurrency)
17. Jenkins
18. XML
19. LWM2M
20. SQS
21. AMQP
22. Kafka
23. AWS (Amazon Web Service)
24. Microsoft Azure
25. I²C
26. SPI
27. Asynchronous serial/UART programming
28. Linux Kernel and Driver development
29. 
    

Pointer to certain address in memory

In embedded system where we are working with microcontroller, many times we find a scenario where we need to access a memory-mapped register in the MCU.  How do we do that in generic way (for example with GCC compiler)?

The answer is to write it like below:

volatile <type> *<varname> = (<type> *)<address>

For example:

#include <stdio.h>

volatile char *var = (char *)0x1000;

int main()
{
    if (*var != 0)
        puts("NOT NULL!");
}

rendered into x86 assembly (64-bit Intel CPU) as:
...
...
.LC0:
        .string "NOT NULL!"

main:
movq var(%rip), %rax      # rax = address of var
movzbl (%rax), %eax         # eax = *var
testb %al, %al
jne .L9
xorl %eax, %eax
ret
.L9:
pushq %rax
movl $.LC0, %edi
call puts
xorl %eax, %eax
popq %rdx
ret

...
.LCOLDE1:
.section .text.startup
.LHOTE1:
.globl var
.data
.align 8
.type var, @object
.size var, 8
var:
.quad 4096           # or 0x1000

Deleting duplicate entries and sorting the rest

I learned an interesting (and very easy) way to remove duplicate entries as well as to sort them. Basically, in C++ it is achieved by creating a new set and initialize with values from the vector.  We shift all the hardwork to the std library to do this.

#include <iostream>
#include <vector>
#include <set>


void print(std::vector<int> &v)
{
    std::cout << "[";
    for(std::vector<int>::iterator it = v.begin(); it != v.end(); ++it)
    {
        std::cout << *it << ",";
    }
    std::cout << "]" << std::endl;
}


void print(std::set<int> &v)
{
    std::cout << "{";
    for(std::set<int>::iterator it = v.begin(); it != v.end(); ++it)
    {
        std::cout << *it << ",";
    }
    std::cout << "}" << std::endl;
}



int main()
{
    int inits[] = {1,10,3,2,2,4,4,5,6,7,8,8,9};
    std::vector<int> vec(inits, inits + sizeof(inits)/sizeof(inits[0]));
    print(vec);
    std::set<int> ves(vec.begin(), vec.end()); // both sorted & unique already
    print(ves);
}