@nicibume I have another idea. Please use the latest version of NNabla, but update the NNabla C Runtime Library used by Spresense.

To do this:

- Update NNabla C Runtime Library:

```
$ cd externals/nnablart/nnabla-c-runtime
$ git fetch
$ git rebase origin/master
```

- Update nnablart Makefile:

```
diff --git a/externals/nnablart/Makefile b/externals/nnablart/Makefile
index cb136a93..1182ad5b 100644
--- a/externals/nnablart/Makefile
+++ b/externals/nnablart/Makefile
@@ -56,7 +56,7 @@ CFLAGS += -std=c99
CFLAGS := $(patsubst -O%,-O3,$(CFLAGS))
-CSRCS = accessor.c list.c shape.c
+CSRCS = accessor.c fixedpoint.c list.c shape.c
ROOTDEPPATH = --dep-path $(SRCDIR)/functions/utilities
VPATH = $(SRCDIR)/functions/utilities
@@ -73,7 +73,7 @@ CSRCS += binary_tanh.c binary_sigmoid.c binary_connect_affine.c binary_weight_
ROOTDEPPATH += --dep-path $(SRCDIR)/functions/implements/quantization
VPATH += $(SRCDIR)/functions/implements/quantization
-CSRCS += add_scalar.c arithmetic.c arithmetic_generic.c div2.c mul2.c mul_scalar.c
+CSRCS += add_scalar.c arithmetic.c arithmetic_fixed.c arithmetic_generic.c div2.c mul2.c mul_scalar.c
CSRCS += pow2.c pow_scalar.c r_div_scalar.c r_pow_scalar.c r_sub_scalar.c
CSRCS += sub2.c add2.c
ROOTDEPPATH += --dep-path $(SRCDIR)/functions/implements/arithmetic
@@ -92,11 +92,11 @@ CSRCS += pooling.c max_pooling.c sum_pooling.c average_pooling.c unpooling.c d
ROOTDEPPATH += --dep-path $(SRCDIR)/functions/implements/neural_network
VPATH += $(SRCDIR)/functions/implements/neural_network
-CSRCS += affine.c affine_generic.c
+CSRCS += affine.c affine_fixed8.c affine_fixed16.c affine_generic.c
ROOTDEPPATH += --dep-path $(SRCDIR)/functions/implements/neural_network/affine
VPATH += $(SRCDIR)/functions/implements/neural_network/affine
-CSRCS += convolution.c convolution_generic.c convolution_float.c convolution_common.c
+CSRCS += convolution.c convolution_generic.c convolution_float.c convolution_int8.c convolution_int16.c convolution_common.c
CSRCS += binary_connect_convolution.c binary_weight_convolution.c depthwise_convolution.c
ROOTDEPPATH += --dep-path $(SRCDIR)/functions/implements/neural_network/convolution
VPATH += $(SRCDIR)/functions/implements/neural_network/convolution
diff --git a/externals/nnablart/nnabla-c-runtime b/externals/nnablart/nnabla-c-runtime
index c58c11dd..a5fb10ea 160000
--- a/externals/nnablart/nnabla-c-runtime
+++ b/externals/nnablart/nnabla-c-runtime
@@ -1 +1 @@
-Subproject commit c58c11ddd182e8ed04eb931bbf2a82f190874c9d
+Subproject commit a5fb10ea5f2e4915fc68823500d4308ab98eb473
```

Please let me know if it worked for you.

Best Regards,

Kamil Tomaszewski