Purpose of the TRST and Power pin on Blackpill design #1953
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Current generation Black Magic Probe itself does not expose or provide ~TRST, only ~RST which is what the iRST_SENSE line is about. ~TRST is the JTAG Test Reset pin and is only found on some pinouts for JTAG (excluding ARM's 10-pin pinout, but such as their older pre-trace 20-pin pinout). This pin only resets the JTAG state machine, which is usually achieved via clocking the same state machine with TCK while holding TMS high for at least 5 cycles. The design of the JTAG state machine guarantees this is the exact same operation as pulsing ~TRST would be. You are correct that power control is achieved on BMP via the PWR_BR line. Do note that for Black Pill, the common code for the platform defines all the critical pinout things expected by those 3 platforms. |
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I was wondering why the version 2.1e schematics would connect the TRST_PIN to the RST pin through a Mosfet. If the TRST_PIN is only useful on pre-Cortex connectors why include it in the design? I do not have access to the schematics for v2.3, so I don't know if this pin is still connected. My projects use small STM32s and clone chips. I've purchased several v2.3 probes from iBitSquared but I also like building my own tools. I have previously built probes using Bluepills and now I want to build one using an STM32F411CE based Blackpill. |
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I'm attempting build a BMP from a Blackpill but I have a few questions concerning the purpose of both the PA6 pin marked TRST and PA1 pin marked Power. I have been referencing the schematic file 'bmpm_v2_1e_schematic.pdf' and I was wondering if the TRST pin is the iRST_SENSE line and the Power pin is the PWR_BR line.
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