This module is part of the original MMBasic library. It is reproduced here with kind permission of Hugh Buckle and Geoff Graham. Be aware it may reference functionality which has changed or is deprecated in the latest versions of MMBasic.¶
Note: Any required file(s) are available in the attachments tab (top right).
' setup the SPI ports for this chip
MCPSetup 1, 2, 3, 4
' demonstration of ramping from one end of the pot to the other
For i = 0 To 100
MCPSet 0, i
Pause 100
Next i
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' driver for the Microchip MCP4xxx series of digital potentiometers
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' initialise the SPI interface
Sub MCPSetup(mosi, miso, clk, ce)
_mosi = mosi
_miso = miso
_clk = clk
_ce = ce
SetPin _mosi, 8 ' set MOSI pin as an output
SetPin _miso, 2 ' set MISO pin as a digital input
Pin(_clk) = 1 : SetPin _clk, 8 ' set CLK pin high then set it as an output
Pin(_ce) = 1 : SetPin _ce, 8 ' set CE pin high then set it as an output
End Sub
' set the potentiometer to a percentage of full scale
' pot = 0 set potentiometer 0
' pot = 1 set potentiometer 1 (not on all chips)
' pot = 2 the default power up setting for potentiometer 0
' pot = 3 the default power up setting for potentiometer 1
Sub MCPSet(pot, percent)
Local junk, r, v
r = pot * (2 ^ 14) ' the bits to select the correct register
v = (256 * percent) \ 100 ' the bits to set the pot
If percent = 100 Then v = &H100 ' full scale
Pin(_ce) = 0 ' select the slave
junk = SPI(_miso, _mosi, _clk, r + v, m, 3, 16)
If pot > 1 Then ' if we are setting the eeprom
Pin(_ce) = 1 ' deselect
Pause 15 ' wait for the write
Pin(_ce) = 0 ' reselect
EndIf
If (SPI(_miso, _mosi, _clk, r + &HC00, m, 3, 16) And &H1FF) <> v Then
Error "Device not responding"
EndIf
Pin(_ce) = 1 ' deselect the slave
End Sub