227 DDS and DAC
227 : DDS and DAC
- Author: Meonwara
- Description: DDS with DAC and analogue output pin
- GitHub repository
- Clock: 40000000 Hz
How it works
Simplistic DDS (accumulator + sinewave lookup table) with resistive DAC to provide analogue output. Board switches control the output frequency.
How to test
With a 40MHz clock selected, change the input switches to some binary value 1-255. Observe a rail to rail sinewave at the analogue pin ua[0].
External hardware
DAC output resistance about 10kOhm. Could add an external capacitor to ground to smooth / filter the waveform.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | ui[0] | uo[0] | uio[0] |
| 1 | ui[1] | uo[1] | uio[1] |
| 2 | ui[2] | uo[2] | uio[2] |
| 3 | ui[3] | uo[3] | uio[3] |
| 4 | ui[4] | uo[4] | uio[4] |
| 5 | ui[5] | uo[5] | uio[5] |
| 6 | ui[6] | uo[6] | uio[6] |
| 7 | ui[7] | uo[7] | uio[7] |
Analog pins
ua | PCB Pin | Internal index | Description |
|---|---|---|---|
| 0 | A4 | 4 | ua[0] |