Designing custom Board

[hamo]

Hello,

for a DIY project including LoRa ra-02, MPU6050 and NEO-6M i have purchased some Blue pills from a vendor but it turned out they are fake blue pills (STM32F103C6).
I am trying to make a RC, so i have a Transmitter which needs 2xSPIs (one for LoRa and one for a TFT Display).
The fake blue pills i have, they do have only 1x SPI therefore i have decieded to design my own Board.

Requirement for the Transmitter:

2xSPIs (LoRa and TFT)

5 channels ADC 

For the Receiver:

1xSPI (LoRa)

1xI2C (MPU6050)

1xUART (NEO-6M)

1xADC (Battery voltage monitoring)

I have searched on the net for a schematic of the Blue pill and found so many but no one with a BOM so i can select the right Materials.

E.g. for the HSE ocsi, there are many 8MHz osci out there but how should i know which one is the right one for my Board.

Is there any form ST hardware design reference or something like that so i can benefit from?

[Andrew Neil]

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@hamo wrote:

Is there any form ST hardware design reference or something like that so i can benefit from?

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Why, yes - there is!

https://www.st.com/resource/en/application_note/an2586-getting-started-with-stm32f10xxx-hardware-development-stmicroelectronics.pdf

On the specific question of oscillators:

https://www.st.com/resource/en/application_note/an2867-oscillator-design-guide-for-stm8afals-stm32-mcus-and-mpus-stmicroelectronics.pdf 

See also:

https://community.st.com/t5/stm32-mcus-products/mems-oscillators-not-compatible-with-stm32f1-and-stm32l1-series/td-p/654210 

You should go to the Product Page for the chip you intend to use, and look on the 'Documents' tab - that will list all the available Application Notes, etc; eg,

https://www.st.com/en/evaluation-tools/nucleo-f103rb.html#documentation 

You can also look at the schematics of ST's boards - go to the Product Page for the board, and look under 'CAD Resources'; eg,

https://www.st.com/en/evaluation-tools/nucleo-f103rb.html#cad-resources 

[Andrew Neil]

Before designing a custom board - especially as a novice - I would very strongly recommend that you prototype & prove your design on an ST board first.

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@hamo wrote:

I am trying to make a RC

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 A what?

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@hamo wrote:

i have a Transmitter which needs 2xSPIs (one for LoRa and one for a TFT Display)

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Can't they share one SPI?

The whole point of a bus like SPI is that it can be shared by multiple devices.

[hamo]

Thank you for the reply.

I have already proved on a breadboard and everything is working.

RC = Radio Controller.

I do not want to share the same SPI between LoRa and TFT on purpose.

Sharing one SPI bus may affect the LoRa sensitivity (i think).

[Andrew Neil]

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@hamo wrote:

Sharing one SPI bus may affect the LoRa sensitivity (i think).

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Eh??

It's just a digital control interface - the LoRa transceiver neither knows nor cares what else is on the bus, surely?

[hamo]

I would prove that on a Breadboard.
Would it make a difference if use SPI with DMA?

[Andrew Neil]

Again, the transceiver neither knows nor cares what is driving the SPI bus - so, as long as you keep within the slave's specifications, it will work.

Beware that solderless breadboards don't have great electrical characteristics - so the issue might no be so much about sharing an SPI per se as about the breadboard wiring ...

[hamo]

Ok, then you suggest i should make a prototype and then prove it.
I think that would be a good idea.

[Andrew Neil]

Definitely.

It is, of course, possible that the 2 devices might not "play nice" together - but they should.