[Request] I2c_hardware.jal : Option for user-selected bus speed

[David VB]

Hi,

I was struggling with an I2C LCD display until I found out on the manufacturer website that, due to a design flaw, the I²C bus speed should be 50 kHz

(for the record: https://support.newhavendisplay.com/hc/en-us/community/posts/9600301114775-NHD-0220D3Z-NSW-BBW-V3-using-I2C-dropping-characters )

My request here is to allow the user to define the sspadd value directly in his application by modifying the following code in i2c_hardware.jal

   -- set correct speed
   if    _i2c_bus_speed == 10 then sspadd = _i2c_1mhz
   elsif _i2c_bus_speed ==  4 then sspadd = _i2c_400khz
   elsif _i2c_bus_speed ==  1 then sspadd = _i2c_100khz
   elsif _i2c_bus_speed ==  0 then sspadd = _i2c_slowest
   else                            sspadd = _i2c_100khz      -- default
   end if

so that the user may override the default 100 kHz value: 

by defining _i2c_bus_speed = 0xFF and initialize sspadd with the needed value in his application

   if _i2c_bus_speed != 0xFF then

     -- set correct speed
       if    _i2c_bus_speed == 10 then sspadd = _i2c_1mhz
        elsif _i2c_bus_speed ==  4 then sspadd = _i2c_400khz
        elsif _i2c_bus_speed ==  1 then sspadd = _i2c_100khz
        elsif _i2c_bus_speed ==  0 then sspadd = _i2c_slowest
        else                            sspadd = _i2c_100khz      -- default
       end if

   end if

What do you think ?

Kind regards,

David

[Rob CJ]

Hi David,

A few suggestions

Option 1

Why not add a value for 50 kHz, although we cannot enter 0.5.

Option 2

Or replace the 100 kHz by 50 kHz?

So instead of:

const _i2c_slowest = 127                           -- (40 kHz @ 20 MHz Fosc)

Use:

const _i2c_slowest  = target_clock / 50_000 / 4 - 1 –- 50 kHz

Option 3

Another option would be to use a user defined constant, for example:

const I2C_USER_BUS_SPEED = 50_000 

And then overrule everything by:

if defined(I2C_USER_BUS_SPEED) then

  spadd =  target_clock / I2C_USER BUS_SPEED / 4 - 1

else

   if    _i2c_bus_speed == 10 then sspadd = _i2c_1mhz

   elsif _i2c_bus_speed ==  4 then sspadd = _i2c_400khz

   elsif _i2c_bus_speed ==  1 then sspadd = _i2c_100khz

   elsif _i2c_bus_speed ==  0 then sspadd = _i2c_slowest

   else                            sspadd = _i2c_100khz      -- default

end if 

Option 3) would be the most flexible.

Kind regards,

Rob

---

Van: jal...@googlegroups.com <jal...@googlegroups.com> namens David VB <pinhe...@gmail.com>
Verzonden: donderdag 4 april 2024 15:30
Aan: jallib <jal...@googlegroups.com>
Onderwerp: [jallib] [Request] I2c_hardware.jal : Option for user-selected bus speed

 

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[Rob CJ]

Hi David,

I added option 3) to the library. Not yet tested and not yet uploaded but can you give it a try.

So define:

const I2C_USER_BUS_SPEED = 50_000 

And give it a try. This version also has the user defined i2c_pins that you can use, solving 2 issues at the same time.

Kind regards,

Rob

---

Van: jal...@googlegroups.com <jal...@googlegroups.com> namens Rob CJ <rob...@hotmail.com>
Verzonden: donderdag 4 april 2024 19:33
Aan: jal...@googlegroups.com <jal...@googlegroups.com>
Onderwerp: Re: [jallib] [Request] I2c_hardware.jal : Option for user-selected bus speed

 

To view this discussion on the web visit https://groups.google.com/d/msgid/jallib/GVXP195MB1637ABCF1E78FC9E3837C64EE63C2%40GVXP195MB1637.EURP195.PROD.OUTLOOK.COM.

[David VB]

Option 3 is definitely to best one !  Thanks Rob !