Implement override of default RTS/DTR behavior for DVM-V24-V2 boards with hardware boot control. #77
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gatekeep
approved these changes
Dec 4, 2024
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DVM-V24-V2 boards have optional hardware boot control, using the CP2102 RTS/DTR signals for BOOT0/RESET respectively. This allows for entering UART boot mode even with a totally corrupted program so you can recover a board without the need for an ST-Link.
Currently in dvmhost (and in most linux terminal applications in general) RTS and DTR are both forced active, which results in the V24 board receiving a valid command to enter UART bootloader mode. These changes override the default behavior and force RTS off, while also sending a second DTR reset pulse. See the scope capture below (BOOT0 is yellow, /RESET is pink).
Ideally, we would avoid the initial RTS & DTR pulses altogether, but there does not appear to be an easy way to achieve this with the current serial implementation.