Unaligned access UsageFault

[gertorro]

Hello, I am trying to use your port of freertos to teensy to build an acquisition system which communicates over Ethernet. I was able to implement many functionalities without any issue. I managed to get UCP communications working without problems, analogRead from the ADC and a simple state machine, all working in separate tasks. I need to read a device attached to the SPI bus, I have tested the read/config code without freertos withou any issues. It also works in the setup() function but the moment I put the read code inside a task I get the following error:

I/O configured and initialised Starting LTC2983 Setup of LTC2983 complete readADC channel 1 state=5 val=-273.15 Ethernet cable is not connected. Ethernet initialised running FreeRTOS kernel V10.4.6. setup(): starting scheduler... Fault IRQ: 0x00000006 sp: 0x2021E5B0 lr: 0xFFFFFFED stacked_r0: 0x00000000 stacked_r1: 0x00000000 stacked_r2: 0x00000001 stacked_r3: 0x403A0000 stacked_r12: 0xA5A5A5A5 stacked_lr: 0x0000B831 stacked_pc: 0x0000C4D4 stacked_psr: 0x41000000 _CFSR: 0x01000000 (UNALIGNED) Unaligned access UsageFault _HFSR: 0x00000000 _DFSR: 0x00000000 _AFSR: 0x00000000 _BFAR: 0x00000000 _MMAR: 0x00000000 Active task (TCB): readTCfro Active task (stack): readTCfro

And the system keeps throwing memory management errors at me. Here is the task's code: static void readTCfromLTC2983(void*) { while (true) { ltc.beginConversion(1); do { ::vTaskDelay(pdMS_TO_TICKS(1'0)); } while (!ltc.isDone()); double val = ltc.readTemperature(1); Serial.print("readADC channel 1 state="); Serial.print(ltc.getState()); Serial.print(" val="); Serial.println(val); Serial.println("Reading temps"); ::vTaskDelay(pdMS_TO_TICKS(500)); } }

I have also tried to access directly the SPI directly without the library for the LTC2983 from inside the task without success. In this case the task is written as: static void readTCfromLTC2983(void) { while (true) { SPI.beginTransaction( SPISettings(2000000, arduino::MSBFIRST, SPI_MODE0)); digitalWrite(10, arduino::LOW); SPI.transfer(LTC298X_SPI_WRITE); SPI.transfer16(LTC298X_ADDR_CMD); SPI.transfer(LTC298X_CMD_BEGIN | 1); digitalWrite(10, arduino::HIGH);/ ::vTaskDelay(pdMS_TO_TICKS(500)); } } And the errors I get are these:

I/O configured and initialised Starting LTC2983 Setup of LTC2983 complete readADC channel 1 state=5 val=-273.15 Ethernet cable is not connected. Ethernet initialised

running FreeRTOS kernel V10.4.6. setup(): starting scheduler... Fault IRQ: 0x00000005 sp: 0x202206D8 lr: 0xFFFFFFFD stacked_r0: 0x0000000A stacked_r1: 0x00000000 stacked_r2: 0x00000001 stacked_r3: 0x403A0000 stacked_r12: 0xA5A5A5A5 stacked_lr: 0x00000259 stacked_pc: 0x0000C58C stacked_psr: 0x21000000 _CFSR: 0x00008200 (PRECISERR) Data bus error (address in BFAR) (BFARVALID) Bus Fault Address Valid _HFSR: 0x00000000 _DFSR: 0x00000000 _AFSR: 0x00000000 _BFAR: 0x403A002C _MMAR: 0x403A002C

Active task (TCB): readTCfro Active task (stack): readTCfro

What could be causing this behaviour? Thanks in advanced!

[tsandmann]

Looks like some data structures of the SPI driver get corrupted. Maybe the stack size of the task is too small? Or SPI is also used from another task? I don't think it's an issue with the FreeRTOS port.

[gertorro]

I managed to get it working by changing the optimization configuration of teensyduino from "Fast" to "Fastest". No issues with the SPI whatsoever and the code works like a charm. Thanks for the wonderful port @tsandmann !!