Timeout on I2C Read Receive Mode if no device is attached

[MaBecker]

Running on a Pico with 2v16.199.

>I2C1.setup({sda: B7, scl : B6});
=undefined
>I2C1.readFrom(0,1)
Uncaught InternalError: Timeout on I2C Read Receive Mode
 at line 1 col 18
I2C1.readFrom(0,1)
                 ^

Which is fine but it takes several seconds until this message is displayed and this is a nogo for a scanner like i2cdect.

Looks like there are some fiexd defs

https://github.com/espruino/Espruino/blob/f2fb0451c25d7ad0afe3bde0f97cf0994a87fbca/src/jshardware.h#L466-L482

https://github.com/espruino/Espruino/blob/f2fb0451c25d7ad0afe3bde0f97cf0994a87fbca/targets/stm32/jshardware.c#L2479

Any hints how to speed this up?

[MaBecker]

>try {
:  print(Date.now());
:  I2C1.readFrom(0,1);
:} catch(err){
:    print(Date.now());
:  print(err);
:}
946687016930.89868164062
946687018927.22033691406
InternalError: InternalError: Timeout on I2C Read Receive Mode
=undefined

[gfwilliams]

Well, these could maybe be lowered a bit (to 1 sec?), but what about using software I2C? does that work?

But potentially if we lower it too much we stop real hardware which does delay its response from functioning correctly.

I feel like i2cdetect is very much a developer tool, it's nothing you'd use in production. I'm not sure it's worth a whole bunch of effort just so the 2 times a year someone uses it, they have to wait 1 minute instead of 13 minutes it takes.

Also, i2cdetect could trivially implement the small bit of i2c needed for a scan, and could just bit-bash it itself - that way it could complete everything very quickly.

[MaBecker]

I just added a WAIT_UNTIL_SHORT for testing

>try {
:  s=Date.now();
:  I2C1.readFrom(0,1);
:} catch(err){
:    print(Date.now()-s);
:  print(err);
:}
2.23254394531
InternalError: InternalError: Timeout on I2C Read Receive Mode

Having a I2C1.detect({start:0,end:0x77}) returning a array of available id's would be great.

[MaBecker]

Any hints would be helpful ;-)

[gfwilliams]

Just try copying the code needed from https://github.com/espruino/Espruino/blob/master/src/jsi2c.c#L66-L164 to do a read, but as JavaScript. Then you have complete control over the delay