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I'm a software engineer who has recently become very interested in hardware. I'm very novice so I apologize ahead of time for any dumb mistakes or misunderstandings I have. This might also be a broad question but I've seemed to be a little lost and could use some direction.

My main project I've been working on is a wearable bluetooth hid controller. As of right now I have been able to connect an attiny85 to an HM-10 bluetooth module to send HID bluetooth commands to my phone using a breadboard.

Now though I want to move from a breadboard and through-hole components to a PCB and surface mount components to try to reduce size and cost. Up until now things have been pretty straightforward thanks mostly due to ( what seems to me ) the bluetooth module abstracting the interaction with the bluetooth chip.

I've been looking at using either a TI cc2541 or a Nordic nRF51822 as a standalone bluetooth chip to put on a PCB in place of using either of these on a module.

Looking at the module it looks like there is more going on then just status leds so I assume that I cant just expect to throw this chip on a PCB with the same connections as I have on the module.

How can I find out what components I need to work directly with the chip rather than the module? Is there a document provided by the manufacturer that lists what other components are required and a schematic as well?

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    \$\begingroup\$ Just opened the nRF51822 datasheet and there is are ~18 schematics and a PCB layout in it. What more do you need? \$\endgroup\$
    – Oldfart
    Jan 10, 2018 at 18:13
  • \$\begingroup\$ I know this may seem dumb, but the datasheet is exactly what I was looking for. It might take a while to comprehend what's on it but you have been helpful. \$\endgroup\$ Jan 10, 2018 at 18:26
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    \$\begingroup\$ If I were you, I wouldn't go the standalone chip way. Because you'd need to take care of the antenna, those QFN chips are hard to solder by hand, the bluetooth stack won't be that easy to develop, and in the end, you'll have an uncertified device that FCC won't be very happy with. You'd rather keep using a module. A lot of commercial products use modules. \$\endgroup\$
    – dim
    Jan 11, 2018 at 16:11
  • \$\begingroup\$ @dimlostfaithinSE Agreed. Maybe tackle other things before you tackle RF. \$\endgroup\$
    – DKNguyen
    Feb 18, 2020 at 5:10
  • \$\begingroup\$ FWIW I ended up using an hm-11 module. \$\endgroup\$ Feb 19, 2020 at 6:12

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There is a plethora of pre-fcc-certified BLE modules that have come out over the past 5 years or so. The RFDuino uses the nrf51822 (as most due to my amazement considering the terribly black box nature of that SOC), as well as the uBlox NINA-B112. Murata makes a really tiny module that is also precertified that makes use of the Dialog Chipset, this Atmel SOC and this Alps SOC (F****** tiny). Best to find the one that best fits your project size and cost goals. Generally speaking, if you can find example firmware from these manufacturers that provides some sort of pass through via a serial bus you should be along pretty quick. Look through the datasheet for mentions of "UART application" or "SPI Slave Operation" or something to that effect and you might find exactly what you need. These modules usually just need clean power, good decoupling and a few pull ups and you are in firmware land.

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Consider a module like the Cypress ezBLE units (http://www.cypress.com/products/ez-ble-and-ez-bt-bluetooth-modules). They have a built in microcontroller (Cortex M0), and all the RF components as well. They come pre-certified so if you ever decide to make a product, you do not need to have it certified yourself. With these, you abstract away the horrible BT stack and potential issues with antenna design. This is probably the best way for you, as it's out of the Arduino playground and into full embedded territory, but not bare metal (in both senses).

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I just came across this question as I am in a similar position for a personal project. I have found it quite confusing with lots of options to pour over, unsure at first which are suitable. I agree that a module is the way to go. In my previous jobs I have seen colleagues implementing their own antennas and balancing networks and it has never been straightforward.

It seems some modules are designed to be an all-in-one with your application running on the module itself, whereas others are designed as co-processors with the application running on a separate microcontroller communicating via UART or SPI.

Having looked into Cypress, Nordic, ST, Microchip and uBlox offerings I have settled on a SiLabs bgx220 module which comes with a UART interface. I found their website was nice and clear with the information, they have good development boards, and their documentation is very good, all of which helps a lot when delving into a new field. They do offer the more capable bgm220 modules too, which are the all-in-one type module and can be the central component in an IoT device.

Hope that helps anybody else in this position.

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