Where Next?

There are a lot of WiFi commands that haven't been covered in this chapter, but now that you have seen examples of most of the basic types and encountered the typical problems that occur you should be able to implement any that you need.

The biggest problem in working with the micro:bit in serial mode it the limited amount of memory. If your program seems to have a tendency to simply "go quiet" on you then suspect that you are creating a ManagedString that is just too large. This is not a big problem when it comes to acting as a server, but it is for a client trying to process a lot of data.

There may also be better ways to handle the serial interaction between the two devices, but the method presented does seem to work reasonably well. If things get in a mess then the retry limits usually reset the entire transaction if you wait long enough.

There is still going to be the occasional unexplained crash and in this case the best solution is to use the soft reset command. It is also worth mentioning that the server program as presented does not actually handle multiple connections. It has to finish dealing with one connection before it can deal with the next.

Complete Listing

#include "MicroBit.h"
MicroBit uBit;
void initWiFi();
int ATWiFi();
int find(ManagedString c, ManagedString s);
void debug(ManagedString s);
//Comment out for V2
#define Tx MICROBIT_PIN_P0
#define Rx MICROBIT_PIN_P1
//
/*  Uncomment for V2
#define baud setBaudrate
#define USBTX uBit.io.usbTx
#define USBRX uBit.io.usbRx
#define Tx uBit.io.P0
#define Rx uBit.io.P1
*/
#define DEBUG 1
#include "MicroBit.h"
void initWiFi();
int ATWiFi();
int resetWiFi();
int setUARTWiFi();
int scanWiFi();
int getIPWiFi();
int modeWiFi(int mode);
int connectWiFi(ManagedString ssid, ManagedString pass);
int getWebPageWiFi(ManagedString URL,
                           ManagedString page);
int getVersionWiFi();
int startServerWiFi();
int waitForWiFi(ManagedString target, int retry, 
                           int pause);
int find(ManagedString c, ManagedString s);
void debug(ManagedString s);
int main()
{
    uBit.init();
    initWiFi();
    modeWiFi(1);
    connectWiFi("ssid", "password");
    getIPWiFi();
    startServerWiFi();
    release_fiber();
}
void initWiFi()
{
    uBit.serial.redirect(Tx, Rx);
    uBit.serial.baud(115200);
    uBit.serial.setRxBufferSize((uint8_t)+500);
}
int ATWiFi()
{
    uBit.serial.send("AT\r\n", SYNC_SPINWAIT);
    return waitForWiFi("OK", 150, 10);
}
int getVersionWiFi()
{
    uBit.serial.send("AT+GMR\r\n", SYNC_SPINWAIT);
    return waitForWiFi("OK", 200, 10);
}
int resetWiFi()
{
    uBit.serial.send("AT+RST\r\n", SYNC_SPINWAIT);
    return waitForWiFi("OK", 1000, 10);
}
int setUARTWiFi()
{
    uBit.serial.send("AT+UART_CUR=115200,8,1,0,0\r\n",
                                   SYNC_SPINWAIT);
    return waitForWiFi("OK", 200, 10);
}
int scanWiFi()
{
    uBit.serial.send("AT+CWLAP\r\n", SYNC_SPINWAIT);
    return waitForWiFi("OK", 500, 50);
}
int modeWiFi(int mode)
{
    ManagedString cmd = "AT+CWMODE_CUR=" +
         ManagedString(mode) + "\r\n";
    uBit.serial.send(cmd, SYNC_SPINWAIT);
    return waitForWiFi("OK", 200, 10);
}
int connectWiFi(ManagedString ssid, ManagedString pass)
{
    ManagedString cmd = "AT+CWJAP_CUR=\"" + ssid + 
                      "\",\"" + pass + "\"\r\n";
    uBit.serial.send(cmd, SYNC_SPINWAIT);
    return waitForWiFi("OK", 200, 20);
}
int getIPWiFi()
{
    uBit.serial.send("AT+CIFSR\r\n", SYNC_SPINWAIT);
    return waitForWiFi("OK", 200, 10);
}
int getWebPageWiFi(ManagedString URL, ManagedString page)
{
    ManagedString cmd = "AT+CIPSTART=\"TCP\",\"" +
                         URL + "\", 80\r\n";
    uBit.serial.send(cmd, SYNC_SPINWAIT);
    if (waitForWiFi("OK", 100, 20) == 0)
        return 0;
    ManagedString http = "GET " + page +
           "HTTP/1.0\r\nHost:" + URL + "\r\n\r\n";
    cmd = "AT+CIPSEND=" + ManagedString(http.length()) +
                                       "\r\n";
    uBit.serial.send(cmd, SYNC_SPINWAIT);
    int retry;
    ManagedString s;
    s = "";
    retry = 40;
    do
    {
        uBit.sleep(100);
        s = s + uBit.serial.read(500, ASYNC);
        retry--;
    } while (find(">", s) == 0 && retry != 0);
    uBit.serial.send(http, SYNC_SPINWAIT);
    retry = 100;
    do
    {
        uBit.sleep(100);
        s = s + uBit.serial.read(500, ASYNC);
        retry--;
    } while (s.length() < 500 && retry != 0);
    if (DEBUG)
        debug("\n\rPage\n\r" + s + "\n\r");
    return 1;
}
int startServerWiFi()
{
    uBit.serial.send("AT+CIPMUX=1\r\n", SYNC_SPINWAIT);
    if (waitForWiFi("OK", 100, 20) == 0)
        return 0;
    uBit.serial.send("AT+CIPSERVER=1,80\r\n", 
                                        SYNC_SPINWAIT);
    if (waitForWiFi("OK", 100, 20) == 0)
        return 0;
    ManagedString s;
    for (;;)
    {
        s = "";
        do
        {
            uBit.sleep(100);
            if (s > 500)
                s = "";
            s = uBit.serial.read(500, ASYNC);
        } while (find("+IPD", s) == 0);
        if (DEBUG)
            debug("\n\rClient Connected\n\r" + 
                                      s + "\n\r");
        int b = find("+IPD", s);
        s = s.substring(b + 1, s.length());
        b = find(",", s);
        s = s.substring(b + 1, s.length());
        b = find(",", s);
        ManagedString id = s.substring(0, b);
        if (DEBUG)
            debug("\n\rTCP id:" + id + "\n\r");
        ManagedString headers = "HTTP/1.0 200 OK\r\n";
        headers = headers + "Server: micro:bit\r\n";
        headers = headers + 
                  "Content-type: text/html\r\n\r\n";
        ManagedString html =
            "<html><head><title>Temperature</title></"
            "<head><body>
             {\"humidity\":81%,\"airtemperature\":23.5C}
             </p></body></html>\r\n";
        ManagedString data = headers + html;
        ManagedString cmd = "AT+CIPSEND=" + id + "," +
                 ManagedString(data.length()) + "\r\n";
        uBit.serial.send(cmd, SYNC_SPINWAIT);
        s = "";
        int retry = 40;
        do
        {
            uBit.sleep(100);
            s = s + uBit.serial.read(500, ASYNC);
            retry--;
        } while (find(">", s) == 0 && retry != 0);
        uBit.serial.send(data, SYNC_SPINWAIT);
        if (waitForWiFi("OK", 100, 100) == 0)
            return 0;
        if (DEBUG)
            debug("\n\rData Sent\n\r");
        cmd = "AT+CIPCLOSE=" + id + "\r\n";
        uBit.serial.send(cmd, SYNC_SPINWAIT);
        if (waitForWiFi("OK", 100, 100) == 0)
            return 0;
    }
}
void debug(ManagedString s)
{
    uBit.serial.redirect(USBTX, USBRX);
    uBit.serial.send(s, SYNC_SPINWAIT);
    uBit.serial.redirect(Tx, Rx);
}
int find(ManagedString c, ManagedString s)
{
    int i;
    for (i = 0; i < (s.length() - c.length()); i++)
    {
        if (c == s.substring(i, c.length()))
            break;
    }
    if (i == (s.length() - c.length()))
        return 0;
    return i;
}
int waitForWiFi(ManagedString target, int retry,
                                         int pause)
{
    ManagedString s;
    do
    {
        uBit.sleep(pause);
        if (s.length() > 500)
            s = "";
        s = s + uBit.serial.read(500, ASYNC);
        retry--;
    } while (find(target, s) == 0 && retry != 0);
    if (DEBUG)
        debug("\n\r" + s + "\n\r");
    return retry;
}