 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Microcontroller and PC projects : PicoMite sine waves?
  Page 5 of 5 |
|||||
| Author | Message | ||||
stanleyella Guru  Joined: 25/06/2022 Location: United KingdomPosts: 2129 |
I guess a "scope" is asking too much but you get my idea of simple display a wave.. for laughs. I learnt math is not just for boffins! I tried don't sample until adc>say 1V no joy but not tried bigger sample arrays and searching for start there. I just use a real scope not how trigger works just move it. |
||||
Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
For a DIY scope a Trig input would be very good. When the pin goes low (say, it could be the other way) you take a string of ADC readings, say 1000. Now you have your readings you can close the ADC. now, pick a point, say 200. If your display is 160 pixels wide then plot ADC readings from a(200) to a(360). By changing the 200 value you can pan along the length of the trace. If you plot from 200 to 320 but every alternate value from a() you'll zoom out to fit more waves across the display. If you want the scope to free run then you could restart the ADC from a SETTICK, although there are other ways. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2129 |
I spent lots of time trying sync so any suggestions I will try, thanks. it's nice to see but not a scope but shows mmbasic can be impressive with a few lines of code and the visual stuff you can do is cool. I tried to update the display as fast without blit or sprite. The sine gen stuff you're doing is rocket science :) |
||||
phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2137 |
Another way to see if the ADC has filled its array is to set the last element to an impossible value (eg -1) before starting. In the main loop read it and when it changes the array is full. My preference is to use interrupts only when there is no efficient alternative and as Mick said, when they are used just set a flag and get back to the main loop as fast as possible. If there are multiple interrupts there is a chance a second may occur while processing the first. Then things can get messy. |
||||
| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
Synchronised scans from a free-running timebase are very old now. They were improved by taking a small amount of the incoming signal and applying it to the timebase to attempt to "lock" it. I had great fun building a valve oscilloscope that never really worked well. :) I think I might still have the tube for it somewhere. lol There's nothing like working with +250V HT and -500V EHT to keep you on your toes. :) The beauty of a triggered scan is that there is no synch to worry about. You are detecting a leading edge then triggering the ADC to take time slices of the waveform. Once you have the slices you've finished with the ADC and you can look at any area of the waveform as you are just scaling and/or plotting values from the array. Setting the frequency of the ADC samples lets you take slices of slow or fast waveforms. The waveform is always completely stationary when viewing it. Because you are simply plotting numbers you can do other things: All the slices will be 0-3.3 as they come in so you can scale them to anything you like to make things easier. You can add or subtract a value from all elements prior to plotting to give a vertical shift. You can start your plot from any point in the array to give a horizontal shift. You can put a coloured graticule on the display. You can put vertical rulers on screen, which can be moved and the time difference between them displayed. You can use horizontal rulers to measure voltages in the same way. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2129 |
I just found that it should be math scale samples!(),79/3.3,samples!() to scale 3.3 to 0-79 for the 160x80 display it works edit No I am wrong,sorry Edited 2023-07-03 09:04 by stanleyella |
||||
| Page 5 of 5 |
|||||
 Print this page |
