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lizby
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Joined: 17/05/2016
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Posted: 01:22am 01 Dec 2023

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stanleyella said Anyone used PCF8574AN?

For output:

' i2c_pcf8574.bas
Dim integer k1=&b10101010,k2=&b01010101
SetPin 6,7,i2c
I2C open 100,100
Do
I2C write &h20,0,1,k1: I2C write &h12,0,1,k2: Pause 500
I2C write &h20,0,1,k2: I2C write &h21,0,1,k1: Pause 500
If Inkey$="x" Then Exit
Loop
I2C write &h20,0,1,255: I2C write &h21,0,1,255 ' turn off

Note that it's "inverted"--0 turns on and 1 turns off.

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lizby
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Posted: 01:34am 01 Dec 2023

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stanleyella said Reading the port is simply done by reading GPIOA and GPIOB..andy
Simply?? Thanks for your reply but SIMPLY?? I guess it's Simple when you understand.

Did you try this?

Same port definitions as for writing. Then, at some point (for port B)

I2C WRITE MCP23017,0,2,GPUPB,&h3f ' set weak pullups on all except bits 6&7

then when you read:

I2C WRITE MCP23017,0,1,GPIOB ' set the register to read
I2C READ MCP23017,0,1,inputs ' read the B port

the integer "inputs" will contain the 8 bits of values.

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lizby
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Posted: 01:44am 01 Dec 2023

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stanleyella said Mick.. rpizero as expander.. interesting idea for versatile in/out,

The Raspberry PI RP2040-Zero linked to is not an rpizero. It's just a version of the Pico we've been using--not a Pico PCB, but a PCB with the same RP2040 microprocessor.

Here's a thread on using the Pico as an I/O expander: Pico as serial or i2c client

In one version, you set up the second, client, Pico with serial console, and then just send MMBasic commands as if you were typing at the console.

The tricky part is decoding what you get back if you want to handle inputs.

(But you're very close with the MCP23017--try again and post your entire code here if it doesn't work.)

PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed

Turbo46

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Joined: 24/12/2017
Location: Australia
Posts: 1611

Posted: 01:49am 01 Dec 2023

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Quote entire code

Bill

Keep safe. Live long and prosper.

phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2135

Posted: 06:46am 01 Dec 2023

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If you want a RP2040 as an expander that is cheaper than the RP2040-Zero and has more pins and flash, search AliExpress for "Purple RP2040 USB-C 16MB".

One example
https://www.aliexpress.com/item/1005003199099382.html
From the group on the right select the purple one.
Edited 2023-12-01 16:47 by phil99

Mixtel90

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Joined: 05/10/2019
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Posts: 6798

Posted: 07:53am 01 Dec 2023

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Be very careful with the purple one. It's nowhere near pin compatible with the Pico. The black one is much better. That one is, I think, the YD-RP2040. More or less the same as a Pico but max CPU speed under MMBasic is 252MHz from my experiments. The power pins are a bit different but you can't back-feed into the USB.

You might find the pinout of the purple board to be better as a remote IO, but there are less GND connections so you may have to be careful with the IO speed and board layout.

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

phil99

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Posted: 10:57am 01 Dec 2023

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Quote It's nowhere near pin compatible with the Pico

Quite right, but I mentioned it as an alternative to the RP2040-Zero as an expander, that is also "nowhere near pin compatible".
Mine runs happily at 378MHz and so far no issues with I/O speed. To minimise the problems caused by so few ground pins one is dedicated to the ADC pins.

Mixtel90

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Posted: 01:05pm 01 Dec 2023

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Here's my current prototype controller using the RP2040-Zero. I needed a small PCB area device and I hadn't got any Micromites! It's in address config mode here (magenta light). You press a colour key to set the address to one of 4 different I2c addresses. Communication is via 5 registers (at the moment).
R0 - config
R1 - 4 direction bits for the joystick and 4 direction bits for the colour buttons
R2 - the two black buttons and the joystick switch. Intending to add two more buttons and two trigger buttons on the final build.
R3 - Joystick X-axis analogue value 0-255 (approx.)
R4 - Joystick Y-axis analogue value 0-255 (approx.)

Two bits of R0 tell the controller how many registers to send on a Read command:
00 - just R1
01 - R1 & R2
10 - R2, R3 & R4
11 = R1, R2, R3 & R4
Reducing the number of messages increases the read speed, obviously. :)

The LED normally indicates the channel colour that it's using. This is saved using VAR SAVE so it returns to the same channel next time it's used.

I've not done the I2C comms on this yet, but I did on an earlier breadboard prototype so I know it can be done reasonably easily.
Edited 2023-12-01 23:07 by Mixtel90

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

lizby
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Joined: 17/05/2016
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Posts: 3150

Posted: 04:49pm 01 Dec 2023

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Here is working code, working hardware:

' MCP23017_IO.bas

Const mcp23017 = &h20 ' A2, A1, A0, R/W all connected to 0V
Const i2caddr=mcp23017
Const IODIRA = &h00 ' Port A IO Direction register DEFAULT = I/P
Const IODIRB = &h01 ' Port B IO Direction register DEFAULT = I/P
Const IOCON = &h0A ' IO Expander config register--address &h0B accesses same register
Const GPIOA = &h12 ' Port A General purpose register
Const GPIOB = &h13 ' Port B General Purpose register
Const OLATA = &h14 ' Port A latch register
Const OLATB = &h15 ' Port B latch register
Const GPUPB = &h0D ' Port B pull-up register

'I2C2 open 100, 1000
I2C2 WRITE MCP23017,0,2,IODIRA,0 ' set direction to output
I2C2 WRITE MCP23017,0,2,IODIRB,255 ' set direction to input
I2C2 WRITE MCP23017,0,2,GPUPB,&hff ' set weak pullups on all bits

mcp17

Pause 1000
Do
mcp17in
Loop

Sub mcp17
Print "write to mcp23017"
For i = 1 To 6
I2C2 Write MCP23017,0,2,OLATA,&b10101010 '
' I2C2 Write MCP23017,0,2,OLATB,&b01010101 '
Pause 1000
I2C2 Write MCP23017,0,2,OLATA,&b01010101 '
' I2C2 Write MCP23017,0,2,OLATB,&b10101010 '
Pause 1000
Next i
I2C2 Write MCP23017,0,2,OLATA,0 ' turn all off
'I2C2 Write MCP23017,0,2,OLATB,0 ' turn all off
Pause 1000
End Sub

Sub mcp17in
I2C2 write MCP23017,0,1,GPIOB
I2C2 read MCP23017,0,1,portabits
Text 0,20,Bin$(portabits,8)
Print Bin$(portabits,8)
I2C2 Write MCP23017,0,2,OLATA,portabits
Pause 3000
End Sub

Edited 2023-12-02 02:51 by lizby

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PhenixRising
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Joined: 07/11/2023
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Posted: 06:53pm 01 Dec 2023

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stanleyella said Mick.. rpizero as expander.. interesting idea for versatile in/out,

Oh, absolutely...it's a no-brainer when you think that you can command the outs to be PWM'd, etc.

And for those smart enough (not me) to use the PIO....unlimited possibilities.

stanleyella

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Joined: 25/06/2022
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Posts: 2129

Posted: 12:28am 02 Dec 2023

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Happy days, input works and all b0 to b7 work as input if grounded.
They are normally high from the weak pull up but it seems you can invert them so grounding makes them high. Interrupt on pin change next :)
credit to lizby and andy but all help was appreciated, thanks.

OPTION EXPLICIT
OPTION DEFAULT NONE

dim integer portabits

const mcp23017 = &h20 ' A2, A1, A0, R/W all connected to 0V
Const i2caddr=mcp23017
const IODIRA = &h00 ' Port A IO Direction register DEFAULT = I/P
const IODIRB = &h01 ' Port B IO Direction register DEFAULT = I/P
const IOCON = &h0A ' IO Expander config register - address &h0B accesses same register
const GPIOA = &h12 ' Port A General purpose register
const GPIOB = &h13 ' Port B General Purpose register
const OLATA = &h14 ' Port A latch register
const OLATB = &h15 ' Port B latch register
const GPUPA = &h0C ' Port C pull-up register
const GPUPB = &h0D ' Port B pull-up register
'
I2C WRITE MCP23017,0,2,IODIRA,255 ' set direction to input
I2C WRITE MCP23017,0,2,IODIRB,255 ' set direction to input
I2C WRITE MCP23017,0,2,GPUPB,&hff ' set weak pullups on all
'
Font 2
CLS
'
Do
'then when you read:
I2C WRITE MCP23017,0,1,GPIOB ' set the register to read
I2C READ MCP23017,0,1,portabits ' read the B port

text 0,20,bin$(portabits,8)
Pause 100
Loop

maybe I was lucky that chips I got read all ports as inputs.
ps works at full over clock.

Edited 2023-12-02 11:08 by stanleyella

Mixtel90

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Posts: 6798

Posted: 08:00am 02 Dec 2023

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I think the main problems with bit 7 arise when you are using pulse train or square wave inputs. I've not done that much research on it, but others have seen missing pulses on that bit whereas they are perfect on the other inputs. Low speed buttons etc. might be ok, but if you do see problems at least you'll have the comfort of knowing that it doesn't have to be your wiring. :)

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

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