#stm32f429

In my recent project, I'm using STM32F429i Cortex M4 with FPU, and I need a Signal Processing Library. So I decided to use ARM CMSIS DSP Software Library, and try Complex FFT Frequency Bin Example. My configuration as follow.

- STM32F429i Discover Board - Emblocks IDE 2.30 - ARM GCC Compiler 4.7 (Emblocks - bare-metal) - Compiler options with harf-FPU (-mfloat-abi=hard) - CMSIS library "libarm_cortexM4lf_math.a" Unfortunately, the original example did not terminated successfully, and falled into hard fault. After some investigation, I figured out the problem is related with bit reversing flag. When the example without bit reversing terminates successfuly, ofcource it is not useful. The reason of this problem is the pre-built GCC library has not the function "arm_bitreversal_32", because a reason regarding the source written in assembly language. So in my situation following workaround succeeded.

Re implement the function "arm_bitreversal_32" with another name like that "sg_bitreversal_32" for avoiding to call original bit reversing function, the code as follow

;/** ;  ****************************************************************************** ;  * @file    sg_bitreversal_32.S ;  * @author  ierturk @ StarGate ;  * @version V1.0.0 ;  * @date    24-May-2014 ;  * @brief   Re implement bit reversal ;  ****************************************************************************** ;  * @attention ;  * ;  * <h2><center>© COPYRIGHT 2014 SarGate Inc</center></h2> ;  * ;  * Unless required by applicable law or agreed to in writing, software ;  * distributed under the License is distributed on an "AS IS" BASIS, ;  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. ;  * See the License for the specific language governing permissions and ;  * limitations under the License. ;  * ;  ****************************************************************************** ;*/     .syntax unified     .thumb     .global sg_bitreversal_32 sg_bitreversal_32:     ADDS     r3,r1,#1     CMP      r3,#1     IT       LS     BXLS     lr     PUSH     {r4-r9}     ADDS     r1,r2,#2     LSRS     r3,r3,#2 sg_bitreversal_32_0:     LDRH     r8,[r1,#4]     LDRH     r9,[r1,#2]     LDRH     r2,[r1,#0]     LDRH     r12,[r1,#-2]     ADD      r8,r0,r8     ADD      r9,r0,r9     ADD      r2,r0,r2     ADD      r12,r0,r12     LDR      r7,[r9,#0]     LDR      r6,[r8,#0]     LDR      r5,[r2,#0]     LDR      r4,[r12,#0]     STR      r6,[r9,#0]     STR      r7,[r8,#0]     STR      r5,[r12,#0]     STR      r4,[r2,#0]     LDR      r7,[r9,#4]     LDR      r6,[r8,#4]     LDR      r5,[r2,#4]     LDR      r4,[r12,#4]     STR      r6,[r9,#4]     STR      r7,[r8,#4]     STR      r5,[r12,#4]     STR      r4,[r2,#4]     ADDS     r1,r1,#8     SUBS     r3,r3,#1     BNE      sg_bitreversal_32_0     POP      {r4-r9}     BX       lr ;/************************ (C) COPYRIGHT StarGate Inc *****END OF FILE****/

Declare the new function in the C code as follow

extern void sg_bitreversal_32(         uint32_t * pSrc,         const uint16_t bitRevLen,         const uint16_t * pBitRevTable);

do FFT without bit reversing as follow

    ....     uint32_t doBitReverse = 0;     ....     arm_cfft_f32(&arm_cfft_sR_f32_len1024, testInput_f32_10khz, ifftFlag, doBitReverse);

do bit reversing as follow

    sg_bitreversal_32((uint32_t *)fftBuf, arm_cfft_sR_f32_len1024.bitRevLength, arm_cfft_sR_f32_len1024.pBitRevTable);

If everything went well so far, modified example as described above should run as the original one with prebuilt library. Please feel free to contact us if you have any further question.

References

STM32F429i Discover Board

Emblocks IDE 2.30

ARM CMSIS library

Frequency Bin Example

GNU Tools for ARM Embedded Processors