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mask output data checksum to 2 bytes#136

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ThomasAkam merged 1 commit intopyControl:masterfrom
alustig3:dev
Feb 24, 2025
Merged

mask output data checksum to 2 bytes#136
ThomasAkam merged 1 commit intopyControl:masterfrom
alustig3:dev

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@alustig3 alustig3 commented Feb 21, 2025

I ran into an error after upgrading to Micropython v1.24

One of our tasks has many variables, and as a consequence the "content" of the variable run_start message is very long:

0.000	variable	run_start	{"in_purgatory___": false, "blocks": [[1, ["LLR", 300, 1.0, true, false], ["RRL", 300, 1.0, true, false]]], "left_dwell_range": [30, 50], "current_trial___": 1, "L_low_vol_warning_sent___": false, "trials_until_change": 0, "block_index___": -1, "match_dict___": {"prediction": "L"}, "treat_volume": 150, "reward_sequences___": [], "outcome___": "", "syringeL___": 0, "syringeR___": 0, "background_reward": [150, 0], "center_dwell_range": [30, 50], "subject___": null, "tone": "none", "right_dwell_range": [30, 50], "task_version___": 20240206, "chosen_side___": "", "outcome_delay_increase_params": [false, 50, 5000], "outcome_delay": 0, "do_increment_block_index___": true, "outcome_delay_blink_freq": 15, "R_low_vol_warning_sent___": false, "api_class": "Sequence_api", "custom_controls_dialog": "sequence_gui", "block_lengths": [300, 10]}

This long message has a checksum value that is greater than 2 bytes. Previously, the to_bytes(2, "little") would only convert the lower 2 bytes, but after the upgrade, I was getting the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pyControl/framework.py", line 175, in run
  File "pyControl/framework.py", line 91, in output_data
OverflowError: buffer too small

In version 1.24 release notes it's noted that there are now buffer size checks

bare-arm, minimal: fix int.to_bytes() buffer size checks

The small change in this commit prevents the error by masking everything off but the last 2 bytes for the checksum. The computer side code that is receiving the serial message is already using a similar mask when checking the checksum:

code/source/communication/pycboard.py

Line 488 in c5b6999

if checksum == message_sum & 0xFFFF: # Checksum OK.

@alustig3 alustig3 changed the base branch from master to dev February 21, 2025 23:55
@alustig3 alustig3 changed the base branch from dev to master February 21, 2025 23:55
@ThomasAkam ThomasAkam merged commit cef428d into pyControl:master Feb 24, 2025
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ThomasAkam commented Feb 24, 2025

Thanks Andy!

@alustig3 alustig3 mentioned this pull request Feb 26, 2025
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@alustig3 alustig3 deleted the dev branch March 23, 2025 23:33
IsabelDAlessandro pushed a commit to IsabelDAlessandro/pycontrol_code that referenced this pull request Jan 21, 2026
@alustig3
make sure checksum is only 2 bytes (pyControl#136)
82da1bc 
Fixes error that occurs with Micropython version 1.24 if the checksum value for messages is greater than 2 bytes.
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@alustig3 @ThomasAkam