mcp23017 setting a single bit on PORTA

[Gert Klemmensen]

Hi,
Just started playing with mcp23017 and everything works fine and easy.
It works well to send a byte that sets the entire port.

But I simply can't figure out how to set a single bit at a time, e.g. bit 7 on port A

Can someone give me a clue?

Kind regards
Gert

[Chris Roper]

Read the Port OR it with a Mask containing the bits you wish to set and Write the result back to the Port.

[Gert Klemmensen]

Hi Chris,

Thank you very much for your reply.
The reason for my question is that as far as I can see the option is already in the mcp23017.h library.
I just can't figure out how to use that command.

Unfortunately, I can't really find a demo or documentation where it says how to use the command.

When I look in the mcp23017.h library, it is these lines that make me think that I should be able to set one bit at a time.

' ==============================================================================
' Programma un solo bit della porta A
' Program only one bit of port A
' ------------------------------------------------------------------------------
Sub OUT_GPA_BIT(In DeviceAddress, In BIT_A, In State_Bit)
DataGpAByte = IN_GPA_BYTE (DeviceAddress)
DataGpAByte.BIT_A = State_Bit
OUT_GPA_BYTE (DeviceAddress, DataGpAByte)
End Sub

Kind regards
Gert

[Chris Roper]

Hi Gert,

I have no idea who created that library and I don't have access to it on this PC but, from that code I would try:
if you wanted to set bit 7 to High for example:

OUT_GPA_BIT(mcp23017Address, 7, HIGH)

[Gert Klemmensen]

Hi Chris,

I have tried with your suggestion. And everything else that occurred to me. But without success.

[Anobium]

Ping the library writer. JackJames I believe.

[Gert Klemmensen]

Thanks for your suggestion Anobium.

Can you help me with a solution to my problem @jackjames

[jackjames]

@Gert:

Sub OUT_GPA_BIT(In DeviceAddress, In BIT_A, In State_Bit)

[Gert Klemmensen]

@jackjames :
I'm still struggling to get it to work.

Tried different things and after switching to hardware i2c I get two errors when I compile my program.

The first one in line 213: HI2reCStart
So I changed this to: HI2CStart is that right or should it be HI2CRestart?

The second in line 419: STATE_BIT is not a bit or valid constant. Constant values should be 0 or 1
I inserted a line with: DIM STATE_BIT as Bit

After these changes it compiles without errors. But still can't get the command to work.

[jackjames]

@Gert:
Hi, I'm out of Rome these days for the holidays.
I return to Rome on January 7th, so as soon as I can I'll check the source of the lines you pointed out to me.
I check, test and possibly release a new corrected version.

[Gert Klemmensen]

@jackjames

It is really appreciated. Many thanks!

[stan cartwright]

an old example
;328p nano controlling two 28BYJ-48 Stepper Motors using interrupt

chip mega328p,16

include <mcp23017.h></mcp23017.h>

option Explicit

#define I2C_MODE Master
#define I2C_DATA PORTC.4
#define I2C_CLOCK PORTC.5
#define I2C_DISABLE_INTERRUPTS ON
'Optionally, you can reduce the I2C timings.
#define I2C_BIT_DELAY 0 us
#define I2C_CLOCK_DELAY 1 us
#define I2C_END_DELAY 0 us

define MCP23017_addr 0x4e

;#define MCP23017_IODIRA 0; make porta output
MCP23017_sendbyte (MCP23017_addr,MCP23017_IODIRA,0) ;set port a to out
;MCP23017_sendbyte(MCP23017_addr,MCP23017_GPIOA,0)

dim lmotdir,lmotor,rmotdir,rmotor,lmotval,rmotval as byte
lmotdir=255:lmotor=1:rmotdir=255:rmotor=1

;interrupt drives motor 100 Hz
; On Interrupt Timer0Match1 Call motors

Dim OCR0  AS byte alias OCR0A
Dim TCCR0 AS  byte alias TCCR0B
WGM01 = 1                'Timer in CTC mode - required

OCR0 = 19
TCCR0 = 0x28
TCCR0 = TCCR0 or 0x05

;-------------------------
;

do
lmotdir=255:rmotdir=255
wait 2 s
lmotdir=1:rmotdir=1
wait 2 s
lmotdir=255:rmotdir=1
wait 2 s
lmotdir=1:rmotdir=255
wait 2 s
loop
;----- end
Sub motors
;left stepper motor
if lmotdir>0 then
if lmotdir=1 Then
lmotor++
if lmotor=9 then lmotor=1
else
lmotor---
if lmotor=0 then lmotor=8
end if
; ReadTable lmot,lmotor,lmotval
select case lmotor
case 1
lmotval=128
case 2
lmotval=192
case 3
lmotval=64
case 4
lmotval=96
case 5
lmotval=32
case 6
lmotval=48
case 7
lmotval=16
case 8
lmotval=144
End Select
Else
lmotval=0
end if
;right stepper motor
if rmotdir>0 then
if rmotdir=1 Then
rmotor++
if rmotor=9 then rmotor=1
else
rmotor---
if rmotor=0 then rmotor=8
end if
; ReadTable rmot,rmotor,rmotval
select case rmotor
case 1
rmotval=1
case 2
rmotval=3
case 3
rmotval=2
case 4
rmotval=6
case 5
rmotval=4
case 6
rmotval=12
case 7
rmotval=8
case 8
rmotval=9
End Select
else
rmotval=0
end if
MCP23017_sendbyte (MCP23017_addr,MCP23017_GPIOA,lmotval+rmotval) ;sets porta to lmotval+rmotval
End Sub
;
table lmot
128,192,64,96,32,48,16,144
end table
;
table rmot
1,3,2,6,4,12,8,9
end table

[Gert Klemmensen]

Hi @Stan,

Thank you very much for your example.

I have no problem sending a BYTE to either PORTA or B.

It's when I just want to set a single BIT on, for example PORTA.

[stan cartwright]

durr. can't you mask the bit in a byte. dunno , long time since using gcb :)

[jackjames]

I modified the two routines.
Now it works.
He had no problems with the old compilers.
I ask evan to replace the old library with this updated one.

[Gert Klemmensen]

@jackjames

Just tested it.
Thank you very much!!

[jackjames]

Updated library:

[Anobium]

Here is the merged file from the Build system.

Dates and other non functional changes were in the pipeline.