Introduction.
Developing “Mia,” a talking cat-shaped robot that speaks in various dialects.
So far, we have only provided one-way audio output, but now we would like to start developing a two-way system finally.
In a previous article here, I wrote about connecting an I2S microphone and an ESP32 on a breadboard to verify speech recognition.
This time, I will actually put this wiring on my own board.
I was thinking of adding the INMP441 circuit.
Out of stock, no way!
Add INMP441 (I2S microphone) circuit on EasyEDA
https://jlcpcb.com/partdetail/-INMP441/C9900078338
I tried to look up the model number of the INMP441 module at LCSC to add it, but they were out of stock… I thought that I2S microphones were standard, so they should be available.
https://www.lcsc.com/search?q=inmp441&s_z=n_inmp441
Difference between Consign Part and Pre-order
JLCPCB supports two types of parts when they are out of stock: consign parts and pre-orders.
- Consign Part: Consign means consign. You have to buy INMP441 modules separately and ship them internationally, which is time-consuming and expensive.
- Pre-order: Order from JLCPCB and pay for the parts in advance. It may take a few days to a week to receive the parts, depending on the parts.
Basically, considering international mailing, I think Pre-order is the way to go, so I look for parts that can be pre-ordered.
https://jlcpcb.com/parts/componentSearch?searchTxt=inmp441
We found several items that can be pre-ordered, but the unit price for those starting at 1 minimum is unbelievably high at about 10,000 yen, while the unit price for those starting at 458 minimum is unusually low at $0.0188 (although this is closer to the original price of the parts).
The INMP441ACEZ-R7, which has a lower unit cost, is confirmed to be the very content used in the INMP441 module. With proper footprint design and wiring, it should function as an I2S microphone.
https://jlcpcb.com/partdetail/TdkInvensense-INMP441ACEZR7/C22379536
This time, since we are still in the prototype stage and only ordered the minimum lot of 2 PCBAs to verify if we can actually have two-way voice interaction, even if we pre-order 458 units, we will not use them immediately, since we don’t want to receive the remaining 456 INMP441 units at the same time as the 2 PCBAs, I decided to ask JLCPCB in advance if they would hold the pre-ordered ones for me.
Contact JLCPCB about handling pre-orders
We inquired with the following statement.
Subject: INMP441 Pre-order and PCBA Questions
Dear JLCPCB Support Team,
I hope this message finds you well.
I am planning to place a PCBA order using the INMP441 microphone (Part Number: C22379536), and I would like to clarify a few points before proceeding:
1. If I pre-order 458 units of INMP441ACEZ-R7 (C22379536) and use only 2 units in my initial PCBA order, will the remaining 456 units be securely stored in my personal parts library for future PCBA orders?
Please note that I intend to repeat small-scale prototype orders before moving to mass production. Once functionality is confirmed, I plan to order several hundred fully assembled boards using the remaining parts.
2. Is there any storage time limit or expiration period for unused pre-ordered parts?
3. How long does it typically take for JLCPCB to receive and prepare pre-ordered parts like INMP441ACEZ-R7 before PCB assembly can begin?
4. As of now, I understand that the INMP441 microphone module (assembled module) is out of stock. Could you please confirm?
5. In case INMP441 cannot be used, are there any available **I2S output MEMS microphone modules or chips** in your parts library that are suitable for ESP32-based audio recording or voice communication?
6. Since I would like to avoid the cost and delay of international consignment shipping, I would prefer to use the pre-order option instead of consigned parts. Does this sound like the most practical approach in my case?
Thank you very much for your support, and I look forward to your response.
Best regards,
[Your Name]
Even though I asked a lot of questions, I got a reply in less than 30 minutes. They said they would hold the parts I had pre-ordered and would not be using at this time. Very generous.
Dear customer,
Thanks for reaching out.
1 Yes, after the pre-order is completed, you will then see it in My Inventory---JLCPCB Parts page, the remaining pieces will be stored in your private part lib for later PCBA use. It is so wise of you to first place prototype orders before mass production, that is also what we advise customers to do, testing the samples before mass production would help to reduce the risk of wrong design, part selection, etc.
2 This is no storage time limit from JLC side. As for expiration period, I would suggest you to kindly refer to the datasheet.
3 For most parts, the estimated lead time is 8-15 days, but this is only for reference. For some special part which is difficult to purchase, the lead time may be longer, you can arrange the pre-order a little bit beforehand.
4 Yes, the available stock is 0, you can place a pre-order, and you will get the final quotation and exact lead time after placing the pre-order.
5 For the replacement for INMP441, sorry but we do not provide customers with exact alternative part numbers since we cannot recommend a very suitable one. And we advise you to search in our Assembly Parts Lib to see if there is a part has the same function and can replace it perfectly.
6 Yes, it seems that pre-order is less time and cost consuming compared with consignment. But it is hard to say, let us first see how the pre-order goes.
Any other question, please feel free to let us know.
Best regards,
Once I decided to go ahead with this, I decided to pre-order it.
When I proceeded to the payment screen, I saw the following notation. I see.
The order showed up like this. Waiting for a quote.
Schematic drawing of INMP441
Take a look at the INMP441ACEZ-R7 datasheet.
The Supply Voltage is 1.62-3.63V, indicating that it can work with a 3.3V supply via ESP32.
So, the wiring will be as follows. In ESP32, I²S GPIOs can be set relatively freely, so for SCK, SD, and WS, select GPIOs that are free GPIO pins and do not seem to be crowded with other GPIOs in the wiring.
// INMP441ACEZ-R7 Wiring U1: INMP441ACEZ-R7
Pin 1 (SCK) —> GPIO19 (ESP32 I2S_CLK)
Pin 2 (SD) —> 100kΩ pull-down resistor –> GND –> GPIO17 (ESP32 I2S_DATA_IN)
Pin 3 (WS) —> GPIO16 (ESP32 I2S_WS)
Pin 4 (L/R) —> GND // L channel fixed
Pin 5 (GND) —> GND
Pin 6 (GND) —> GND
Pin 7 (VDD) —> 3.3V // Power supply common to ESP32
Pin 8 (CHIPEN) —> 3.3V // Always ON (10kΩ pull-up is acceptable)
Pin 9 (GND) —> GND
// Power Supply Filter Components
C1: 0.1uF ceramic capacitor between VDD and GND
This time, the MEMS microphone is placed on the back of the board and a hole is drilled from the back of the chassis toward the MEMS microphone to allow sound to be captured. After actual placement and AUTO routing, it was done in one shot.
I’ll make a PCB layout with this, order two PCBAs for prototype verification, and depending on the estimated lead time for incoming INMP441 modules, look for an alternative I2S microphone module.
Incidentally, we contacted the Japanese branch of TDK InvenSense, which sells INMP441 modules, and were told that INMP441 was EOL seven years ago, and if it exists now, it is only sold by Digikey and Mouser, which had purchased small lots.
For I2S microphones, I thought INMP441 was the standard since it was caught in the search, but I heard that it is already different, so I guess I should switch to implement it with an alternative I2S microphone module for INMP441.
INMP441 microphone in the center of the back of the board
INMP441 not in stock.
A day or two later, I received the following e-mail from the JLCPCB.
Mfr.Part # INMP441ACEZ-R7 Quotation failed
Thank you for ordering at JLCPCB. We are sorry to inform you that the below parts are out of stock and unable to get quotation, so the parts have to be cancelled. The refund has been returned to your original payment method. It usually takes several days for the money to arrive.
As I thought, there seems to be no INMP441. So I have no choice but to use another I2S microphone, so I will look for one.
