'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Simon — Thu, 30 Jan 2020 10:12:15 GMT

I've talked around internally and we've came to the same conclusion, that the migration guide for nrfx drivers is misleading. The following statement is not true:

The legacy layer will no longer be supported in future SDK releases.

Also, there is not any reason to migrate to the NRFX drivers, since it will just create an unnecessary hassle and the legacy (nrf_drv..) works well for all intents and purposes. I have pushed internally and will see that the documentation gets updated as soon as possible.

Best regards,

Simon

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Shockel — Tue, 21 Jan 2020 19:18:05 GMT

Well, I stumbled across this migration guide today which actually seems to explain everything: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fstruct_sdk%2Fstruct%2Fsdk_nrf5_latest.html&cp=5_1 . It does state that simple #defining the entries as "0" is insufficient.

@Simon: It would be nice if you could internally come to a consensus. You (and based on other posts I have seen) suggest to stay with the legacy driver, while the migration guide states differently. Please advise.

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Shockel — Thu, 12 Dec 2019 17:54:59 GMT

I am summarizing the great help by Simon since it did get a bit lengthy (all credits of course to Simon !). I found out in the meantime that pretty much the exact same thing applies to SPI as well.

The key was to not use the NRFX drivers directly, and to not get discouraged by the term "legacy driver". "Legacy" is more to be interpreted as "proven and established". Behind the scenes, the legacy nrf_drv_twi.h driver itself uses the NRFX layer. A welcome side effect is then, that simply by setting TWIx_USE_EASY_DMA appropriately, you can switch to the DMA assisted driver (and it appears to me well worth doing so).

Use nrf_drv_twi.h, and add nrfx_twi.c or nrfx_twim.c to your project.

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Simon — Mon, 09 Dec 2019 15:49:04 GMT

I am sorry for not addressing your question right away, I'll try to do that now (go to the bottom to get right to the solution).

Let's go in reverse order:

The macro NRFX_TWI0_INST_IDX is defined in nRF5SDK16\modules\nrfx\drivers\include\nrfx_twi.h:

#ifndef __NRFX_DOXYGEN__
enum {
#if NRFX_CHECK(NRFX_TWI0_ENABLED)
    NRFX_TWI0_INST_IDX,
#endif
#if NRFX_CHECK(NRFX_TWI1_ENABLED)
    NRFX_TWI1_INST_IDX,
#endif
    NRFX_TWI_ENABLED_COUNT
};
#endif

The header file nrfx_twi.h is included from nRF5SDK16\modules\nrfx\drivers\src\nrfx_twi.c:

#if NRFX_CHECK(NRFX_TWI_ENABLED)

#if !(NRFX_CHECK(NRFX_TWI0_ENABLED) || NRFX_CHECK(NRFX_TWI1_ENABLED))
#error "No enabled TWI instances. Check <nrfx_config.h>."
#endif

#include <nrfx_twi.h>
#include <hal/nrf_gpio.h>
#include "prs/nrfx_prs.h"
.
.

For nrfx_twi.h to be included you have to define NRFX_TWI_ENABLED and at least one TWI instance (NRFX_TWI0_ENABLED or NRFX_TWI1_ENABLED)
- Take a look at apply_old_config.h to see how NRFX_TWI_ENABLED is defined:

#if defined(TWI_ENABLED)

#undef NRFX_TWI_ENABLED
#define NRFX_TWI_ENABLED   (TWI_ENABLED && (NRFX_TWI0_ENABLED  || NRFX_TWI1_ENABLED))
#undef NRFX_TWIM_ENABLED
#define NRFX_TWIM_ENABLED  (TWI_ENABLED && (NRFX_TWIM0_ENABLED || NRFX_TWIM1_ENABLED))

TWI_ENABLED has to be defined (=1)
NRFX_TWI0_ENABLED || NRFX_TWI1_ENABLED has to be defined:
- Take a look at apply_old_config.h to see how these are defined:

#if defined(TWI_PRESENT) && !defined(TWIM_PRESENT)

#undef NRFX_TWI0_ENABLED
#define NRFX_TWI0_ENABLED   TWI0_ENABLED
#undef NRFX_TWIM0_ENABLED
#define NRFX_TWIM0_ENABLED  0

#undef NRFX_TWI1_ENABLED
#define NRFX_TWI1_ENABLED   TWI1_ENABLED
#undef NRFX_TWIM1_ENABLED
#define NRFX_TWIM1_ENABLED  0

Solution:

Okay, I see now that this takes too long time too explain in-depth, but I think you can fix the error by setting the following defines accordingly:

TWI_ENABLED 1
TWI0_ENABLED 1
TWI0_USE_EASY_DMA 0
- This will make the TWI drivers use NRFX_TWI0_INST_IDX instead of NRFX_TWIM0_INST_IDX

So when you get any complaints about NRFX twi instance 0 (not twim), then simply enable the legacy instance 0 (TWI0_ENABLED 1 ) and disable dma for that instance (TWI0_USE_EASY_DMA 0)

I hope this solves your issues.

Best regards,

Simon

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Shockel — Mon, 09 Dec 2019 15:09:24 GMT

Actually, Simon, I have to correct something. If I don't use the nrfx driver directly, but instead the nrf_drv_twi, and also properly define the TWI with TWI_ENABLED and also enabling the instance TWI0_ENABLED, then it is not necessary to uncomment the line. And consequently the configuration could be properly made using CMSIS. So the trick was to use the nrf_drv_twi instead of the nrfx driver directly. I'll write a summary so we can have a single answer to the thread.

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Shockel — Mon, 09 Dec 2019 13:39:44 GMT

Thanks for the clarification, Simon. But is it asked too much to put a one-liner into your online documentation where the nrfx twi (and spi) drivers are explained ?

See Software Development Kit -> SDK16 -> Hardware Drivers -> nRF52832 Drivers -> TWI

Modules
Software controlled TWI Master driver
Software controlled TWI Master driver (deprecated).

TWI driver - legacy layer
Layer providing compatibility with the former API. <--- "legacy layer" and "former API" don't suggest this is the preferred method.

TWI driver
Two Wire Interface master (TWI) peripheral driver. <--- this should instead hint that direct use of the nrfx layer is discouraged.

TWI HAL
Hardware access layer for managing the TWI peripheral.

And then secondly, I changed my code to use the nrf_drv_twi instead, and included the nrfx_twi.c as part of my project to link against. My original findings still seem to hold true: in sdk_config.h

// <e> TWI_ENABLED - nrf_drv_twi - TWI/TWIM peripheral driver - legacy layer
//==========================================================
#ifndef TWI_ENABLED
//#define TWI_ENABLED 0
#endif

I had to comment out the TWI_ENABLED line (unless I am doing something wrong elsewhere). For one, we just learned that the "legacy layer" is the preferred layer, so who would guess that you actually have to remove this line from the config file ? (Referring to the title of this entry)

Lastly, you seem to hint (citing the linked references) that it maybe ok to uncomment/remove defines from the sdk_config file. But that is not even possible with the CMSIS config wizard, so maybe it shouldn't be promoted as the config tool, then.

Simon, I am not trying to be difficult. Just painting the picture from the perspective of a new-comer to Nordic. It can be really confusing. Reminds me of the "no pain no gain" motto that some people cherish. I truly appreciate your help.

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Simon — Mon, 09 Dec 2019 10:24:18 GMT

Yes, you have understood it correctly, don't use the NRFX layer directly. The NRFX source files should be included in the project since they are used by the legacy functions.

You can see that the NRFX layer is used similarly in the nRF Connect SDK (one of our newest projects), where Zephyr functions are used as the top layer.

Best regards,

Simon

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Shockel — Sun, 08 Dec 2019 19:47:47 GMT

So if I read the links you provided below, and in particular the definition of "legacy", is the Nordic suggested way then to

* use nrf_drv_twi.h, the "legacy" driver, and to

* include nrfx_twi.c in the project

Ie, to NOT use nrfx_twi.h directly ?

(and similarly use nrf_drv_spi.h together with nrfx_spi.c) ? Or am I confused now ?

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Simon — Fri, 06 Dec 2019 13:21:35 GMT

Take a look at the answer given by Simonr in this thread, where he provides an explanation of why both the NRFX and the legacy layer are present. Einar Thorsrud elaborates on this as well in this thread.

Hopefully, this answers your questions.

Best regards,

Simon

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Shockel — Thu, 05 Dec 2019 15:36:31 GMT

Simon,

I had the impression that the way to configure sdk_config.h was to enable and disable functionality. Even example applications contain both the NRF and the NRFX defines in there. The fact that the pure presence of a define (even if defined as 0) has implications was unexpected to me. I feel example apps should then either contain NRF or NRFX defines. My 2 cents.

RE: 'NRFX_TWI0_INST_IDX' undeclared - possible solution and bug found

Simon — Thu, 05 Dec 2019 15:18:00 GMT

I think the intention is that the legacy definitions should be the dominant ones, meaning that if both TWI_ENABLED and NRFX_TWI_ENABLED are defined, it should always choose TWI_ENABLED. No matter if TWI_ENABLED is set to 0 or 1.

That is the reason #if defined(TWI_ENABLED) is used. It will check if it is defined, and change the NRFX_TWI_ENABLED accordingly.

Best regards,

Simon