This example implements both sync and async i2c depending on the settings below. It was written to facilitate testing of the Espressif's ESP32 i2c_master code.
- Comment or un-comment the
#define I2C_USE_CALLBACKat the top ofi2c-test.cas you wish:-
Uncommented:
- Use async i2c with callback and FreeRTOS task-wakeup.
- Achives ~7500 single-byte samples per second at 400kHz with FreeRTOS systicks at 1000Hz.
- This uses only ~25% CPU overhead, which is quite efficient at that sample rate.
-
Commented:
- Use sync i2c
- Achives ~995 single-byte samples per second at 400kHz with FreeRTOS systicks at 1000Hz. This method is slower because of context switch overhead. If you get ~99 samples/sec, then you are probably running FreeRTOS systicks at 100Hz.
- This uses lots of CPU overhead due to context switch overhead. It could be mitigated by increasing vTaskDelay(1) to something higher, but the sample time would suffer.
-
When running it prints output like the following, with meas/sec stats at the bottom:
=== MALLOC_CAP_8BIT
Heap summary for capabilities 0x00000004:
At 0x4080e9e0 len 449584 free 388036 allocated 58820 min_free 387816
largest_free_block 385012 alloc_blocks 60 free_blocks 1 total_blocks 61
At 0x4087c610 len 12116 free 10348 allocated 0 min_free 10348
largest_free_block 10228 alloc_blocks 0 free_blocks 1 total_blocks 1
At 0x50000000 len 16360 free 14592 allocated 0 min_free 14592
largest_free_block 14580 alloc_blocks 0 free_blocks 1 total_blocks 1
Totals:
free 412964 allocated 58580 min_free 412744 largest_free_block 385000
=== TASK STATS
name run ctr avg %cpu
main 6716371 6
IDLE 70006198 69
Tmr Svc 10 <1
esp_timer 46960 <1
text length=113
=== TASK LIST
Name state prio core? free stack task number
main X 1 0 18560 2
IDLE R 0 0 1320 3
esp_timer S 22 0 3864 1
Tmr Svc B 1 0 1780 4
text length=122
Tasks are reported as blocked (B), ready (R), deleted (D) or suspended (S).
0. 34
meas/sec=7506, last_i2c_event=1 (I2C_EVENT_DONE), i2c_err=0=== MALLOC_CAP_8BIT
Heap summary for capabilities 0x00000004:
At 0x4080e780 len 450192 free 411568 allocated 35992 min_free 410304
largest_free_block 409588 alloc_blocks 54 free_blocks 1 total_blocks 55
At 0x4087c610 len 12116 free 10348 allocated 0 min_free 10348
largest_free_block 10228 alloc_blocks 0 free_blocks 1 total_blocks 1
At 0x50000000 len 16360 free 14592 allocated 0 min_free 14592
largest_free_block 14580 alloc_blocks 0 free_blocks 1 total_blocks 1
Totals:
free 436496 allocated 35776 min_free 435232 largest_free_block 409576
=== TASK STATS
name run ctr avg %cpu
main 33570677 5
IDLE 325726113 50
i2c_task 291773639 44
Tmr Svc 11 <1
esp_timer 46952 <1
text length=147
=== TASK LIST
Name state prio core? free stack task number
main X 1 0 18560 2
IDLE R 0 0 1320 3
i2c_task B 10 0 1496 5
esp_timer S 22 0 3864 1
Tmr Svc B 1 0 1780 4
text length=153
Tasks are reported as blocked (B), ready (R), deleted (D) or suspended (S).
0. 53
meas/sec=992, last_i2c_event=0 (I2C_EVENT_ALIVE), i2c_err=0
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