File content as of revision 1:00109a338de8:

// KeyMatrixAnalyzer for TrackPoint Keyboard USB English 0B47190
#include "mbed.h"

// R1 R7 R6 S9 R4 R5 S0 R2 R3 S5 S1 R0 S2 S4 S7 S8 S6 S3 S12 S13 S14 S11 S10 S15 M0 ML MM MR
const int RPINLEN = 8;
const int SPINLEN = 16;
DigitalIn rpin[RPINLEN] = {p12, p20, p14, p22, p18, p15, p19, p17};
DigitalOut spin[SPINLEN] = {p21, p23, p24, p9, p11, p13, p26, p25, p10, p16, p29, p7, p27, p8, p28, p6};

Serial pc(USBTX, USBRX);

int prevs = -1;
int prevr = -1;

void loop() {
    for (int s = 0; s < SPINLEN; s++) {
        spin[s] = 0;
        wait_ms(5);
        for (int r = 0; r < RPINLEN; r++) {
            if (rpin[r] == 0) {
                if (prevs == s && prevr == r) {
                    continue;
                }
                prevs = s;
                prevr = r;
                pc.printf(" %d %d\r\n", s, r);
            }
        }
        spin[s] = 1;
    }
}

int main() {
    for (int r = 0; r < RPINLEN; r++) {
        rpin[r].mode(PullUp);
    }
    for (int s = 0; s < SPINLEN; s++) {
        spin[s] = 1;
    }

    while (true) {
        loop();
    }
}