How to better design products for on-board burning - single-line serial port articles

In the design, there will always be a special programming line

Nowadays, the chip is getting more and more integrated, the volume is getting smaller and smaller, and even the integrated board is silently comparing the coins:

How to better design products for on-board burning - single-line serial port articles

Figure 1 Core board and coin comparison chart

However, to integrate more functions on such a small number of pins, only the communication line is cut. At this time, the single-line serial interface has its place.

New requirements are coming. Does the existing debugging download tool support the new communication interface? Let's take a recent case to analyze: a foreign customer needs to add a manufacturer's chip programming support. By knowing the programming data of the chip, it is found that there is only one communication pin for programming, but the standard asynchronous Serial interface protocol.

Interface principle of single-line serial port

The so-called single-line serial port (referred to as "single-line asynchronous serial communication interface", referred to as "single-line serial port" in this paper), is used with the standard serial port (full name "standard asynchronous serial communication interface", referred to as "standard serial port" ") The same communication protocol. The only difference is that unlike the two serial data lines (Txd and Rxd), the single-wire serial port has only one data line to provide both transmit and receive functions. Therefore, the single-wire serial port adopts the half-duplex communication mode, and the specific single-line serial port wiring diagram can be referred to FIG.

Single-line serial chip wiring diagram

Figure 2 Single-line serial chip wiring diagram

Only need to access four lines (MOD, /RESET, VCC, GND) to be able to burn perfectly. The foreign-designed communication port (MOD/IO) can also be used to select the working mode, that is, at the same time of power-on reset, the input timing waveform of the MOD pin is detected, thereby entering different working modes, such as single-line serial port programming. Mode, etc. After entering the single-line serial programming mode, the function of the MOD pin is converted to data communication. Master this rule, after AK100Pro connects these four lines, click "burn" on KFlashPro, you can easily achieve burning.

Analyze the programming effect of single-line serial port

Worried about the speed of burning? We use data to illustrate whether it is fast or slow. The chip supports a maximum communication rate of 500000bps, and we use this baud rate for communication. Figure 3 is the timing data when the logic analyzer (LA2532) captures the programming communication:

Data captured by the logic analyzer (LA2532)

Figure 3 Data captured by the logic analyzer (LA2532)

Let me talk about the meaning of the data, the waveform is intercepted in the process of "program + check". For two strings of relatively long data, the shorter one is the burned data. After sending the data, the query status command is sent to wait for the chip to be burned and responded, and then the read command is issued, and the longer is read. The data that came up for verification.

As seen from the figure, the interval between the data read from the read data and the next packet is only 3.5ms. After deducting the official 2ms response time, the AK100Pro takes 2ms for packet parsing, verification and function conversion. Not enough.

to sum up

With a short programming time, a small number of communication lines, and a small footprint, single-line serial products are expected to become popular in the miniaturized wearable market.

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