It Started With a Hardware Limitation I have been using Quectel GNSS modules in my designs for a while. They are reliable, well-documented, and the support ecosystem is solid. But the module I had been using had one problem that I kept running into: no external antenna support . For most projects that is a minor inconvenience. For a marine vessel monitoring and control system , it is a non-starter. A vessel hull blocks sky view, antenna placement is critical, and the difference between a clean fix and no fix at all often comes down to whether you can mount the antenna where it actually has line of sight. An integrated antenna in a sealed enclosure below deck simply does not cut it. So I went directly to Quectel. The Conversation With Quectel I reached out through their official sample request channel. I was not expecting much — most component manufacturers have a standard process: fill out a form, wait, get a few uni...
Now the code has been cut down to less that 30 lines. here is a part of the code...
do{
if(input(pin_a0))
{
test = 0b11011011;
}
else if(input(pin_a1))
{
test = 0b10011001;
}
for(i=0;i<8;i++)
{
value = bit_test(test,i);
output_low(S_CLK);
output_low(L_CLK);
if(value==1)
{
output_bit(Data,1);
output_bit(S_CLK,value);
output_bit(Data,0);
}
else if(value==0)
{
output_bit(S_CLK,1);
output_bit(S_CLK,0);
}
do{
if(input(pin_a0))
{
test = 0b11011011;
}
else if(input(pin_a1))
{
test = 0b10011001;
}
for(i=0;i<8;i++)
{
value = bit_test(test,i);
output_low(S_CLK);
output_low(L_CLK);
if(value==1)
{
output_bit(Data,1);
output_bit(S_CLK,value);
output_bit(Data,0);
}
else if(value==0)
{
output_bit(S_CLK,1);
output_bit(S_CLK,0);
}
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