Been working on a cheap low frequency dual channel USB scope for audio work.
Designed the pcb and got it made.
Got stuck into software for PC and a PIC32mx microcontroller.
Tried clocking a2d at full speed just reading outputs but i twas terribly noisy, must have been trying to read as data was changing.
So clocked a2d in software and read each channel after a2d was clocked.
Much cleaner signal now. But still a bit noisy. Spotted a2d decoupling wasnt close enough so fixed that and nice clean signal now.
However, I was disappointed with max speed of scope being about 3 mega samples/s. I looked up i/o instructions for pic32mx and I found some faster ones. That improved the speed quite a bit. I then spotted an instruction that can set/reset multiple i/o pins at the same time.
This brought up my sampling speed to 11 mega samples/second over two channels.
Designed the pcb and got it made.
Got stuck into software for PC and a PIC32mx microcontroller.
Tried clocking a2d at full speed just reading outputs but i twas terribly noisy, must have been trying to read as data was changing.
So clocked a2d in software and read each channel after a2d was clocked.
Much cleaner signal now. But still a bit noisy. Spotted a2d decoupling wasnt close enough so fixed that and nice clean signal now.
However, I was disappointed with max speed of scope being about 3 mega samples/s. I looked up i/o instructions for pic32mx and I found some faster ones. That improved the speed quite a bit. I then spotted an instruction that can set/reset multiple i/o pins at the same time.
This brought up my sampling speed to 11 mega samples/second over two channels.