Cost review

Newest SDK:

Espressif has moved the SDK to GitHub.  At this point, It is version 2.1.  I have no indication that they have done anything with the ADC Feature I requested.  I have not updated to this newest SDK yet. I will do that before I spend any time working on firmware.

New component costing:

The 74LVC2T45 level shifter chips are US $0.32 each in low quantities.  The PCA9306 I2C level shifter are about US $0.60 each in low quantities.  This results in the costs of the level shift components arount $1.50.  The original single part costs around US $1.25 each in low quantities.  This is not a big difference in cost but it does affect board space.

Design review:

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Target interface analysis

Website security:

I have updated this website to default to TLS for connections.  I have a certificate supplied by my hosting provider.  I have also turned on member accounts.  I am hoping this will make it more convenient you, the readers to join the conversation.

Voltage level shifter:

I am still trying to decide the best way to go for adjusting to the target platform voltage.  SPI typically needs 3 bits output (SS, SCLK, MOSI) and one bit input(MISO)  Sometimes SPI needs more. JTAG needs 4 pins output(TCK, TMS, TDO, TRST) and one bit input(TDI). I found the JTAG signal description on this page. I2C needs two bits of bi-directional open drain signals.  I don’t know of any MicroControllers that can be programmed over I2C but there are flash memories that are programmed that way.

Based on this information, I can see that I would want 4 bits of output and 2 input along with a 2 bit open drain bi-directional.  This gives me a total of eight bits of data available to connect to the target device.  In addition to that, I need Target Vcc and GND and Vpp. Continue reading