How to test PonyProg. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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How to test PonyProg. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Computers

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During the time that has passed since the publication of the description of this programmer in the Radio magazine, many readers have collected and successfully use it. However, incoming questions show that sometimes it is difficult to check the assembled programmer. The fact is that the signals in its circuits are of a pulsed and often non-periodic nature (which, however, is typical for all devices operating under computer control). Even with an oscilloscope, it is quite difficult to verify the correct formation of these signals. The article describes a method for checking the operation of the hardware of a programmer connected to a computer using a multimeter. True, this requires a special program TSOM.

On the scheme of the programmer PonyProg, shown in fig. 1, two of its functional units are shown docked: the main interface unit with the computer's COM port (see "Radio", 2001, No. 6, p. 25, Fig. 2) and the PICmicro microcontroller programming adapter ("Radio", 2001, No. 7, p. 21, Fig. 8). The latter is chosen as the most complex of the adapters, all others contain only a few passive elements.

(click to enlarge)

The names of the circuits of the RS-1 interface are indicated next to the sockets of the XS232 socket of the interface node. Recall that this socket must be directly docked with a nine-pin plug of the computer system unit. Connection using a null-modem cable is unacceptable, and a modem cable, the plug and socket of which are connected one-to-one, can be used if it contains all the ones indicated in Fig. 1 chain, and its length does not exceed 1 m.

It should also be taken into account that the drawing of the printed circuit board of the interface unit (see Fig. 3 in "Radio", 2001, No. 6, p. 25) is given in a mirror image, therefore, before transferring the drawing of conductors to the board blank in the usual way (by tapping centers holes and subsequent application of printed conductors with varnish or waterproof ink), it must be turned over accordingly.

After connecting the programmer to the computer, run the TCOM program. The window shown in Fig. 2. Using the buttons available in it, select the port (COM1 or COM2) to which the programmer is connected. Pressing the on-screen buttons with the mouse is equivalent to pressing the keys on the keyboard corresponding to the underlined letters or numbers in the button labels, together with the Alt key.

How to test PonyProg

If the COM port plug is 25-pin, press the corresponding screen button, replacing the previous window with the window shown in fig. 3. The information given in it can be used to correctly connect the programmer to the 25-pin COM port plug. The program remembers the correspondence between the port number and its connector. It is enough to install it once, and in the future, when you change the port, the image of its connector will automatically appear on the screen.

How to test PonyProg

As you know, a fully "equipped" COM port has three output circuits (TXD, DTR, RTS) and five input circuits (RXD, DSR, CTS, DCD, RI). The TCOM program allows you to set any of the outputs to a high (High) or low (Low) logic level. To change it to the opposite, just press the corresponding screen button. All changes in input signal levels are immediately displayed on the screen.

Checking the programmer begins with the power node. The switch SA1 of the interface node is transferred to the right (according to the diagram) position, thus including the "internal" power supply of the programmable microcircuit from the COM port. The microcircuit itself does not need to be installed in the adapter panel. It is replaced by a 1 kΩ resistor inserted into the panel sockets intended for power outputs (for example, into sockets 14 and 5 of the XS1 panel for PIC16F8x chips). By changing the state of the TXD, DTR and RTS circuits, make sure that the voltage across the resistor does not go beyond 5 ± 0,5 V if the level of any of them is high, and is absent when all of the levels are low. If there is no voltage at a high level at one of the outputs and low at the other two, check the corresponding one of the diodes VD1, VD2.VD4.

If the voltage is less than 4,5 V, there may be two reasons for this. The first one is the integrated regulator DA1 with too high value of the minimum input voltage (for example, the LM78L05 chip stops working when the input voltage is less than 6,7 V). As a replacement for the LM2936Z-5.0 stabilizer indicated on the diagram, we can recommend the LM2931Z-5.0 or the domestic KR1170EN5. For normal operation of these microcircuits, the input voltage must exceed the output voltage by only 0,2 V (typical value).

The second reason is that the computer's COM port is too "weak" to withstand the load. The word "weak" is in quotation marks because, according to the standard, with a load of 3 kOhm, the high and low levels of the output voltage of the port can lie, respectively, in the intervals of +5 ... +15 and -5 ... -15 V. Although traditionally it is believed that in fact they are close to +12 and -12 V, in fact this is far from the case. For most RS-232 driver microcircuits, the typical output voltage levels do not exceed +7,5 ... 8 and -7,5 ... -8 V, and the most modern ones have even less, up to +5,5, 5,5 and -250 V. The trend towards a decrease in the signal span is not accidental: due to this, it is possible to increase the data transfer rate to XNUMX Kbps. If your computer has such a COM port, nothing can be done, you will have to switch to external power.

The latter is achieved simply: it is enough to apply a voltage of 1 V from an external source to the connector X12 of the interface node and switch the SA1 switch to the position shown in the diagram. The supply voltage of the programmable microcircuit in this mode should also be within 5 ± 0,5 V, turn on the high level of any of the TXD, DTR, RTS signals and turn off when the level of all three is low. If this is not the case, check the operation of the electronic key on transistors VT1, VT2 in the interface unit.

Next, they check the operation of the node that supplies the programmable microcircuit with voltage, which puts it into programming mode. It is measured between slots 4 and 5 of panel XS1 (PlC16F8x). Don't forget to set switch SA1 of the adapter to the position corresponding to the power supply mode: upper (according to the diagram) if the power is external, lower - when powered from the port. In the first case, the GB1 battery may be absent, in the second, it is required.

The programming voltage should turn on when the TXD circuit is driven high and turned off when driven low. Its value can be in the range of 9 ... 13,5 V. If problems arise, check the electronic key on transistors VT1, VT3 and the zener diode VD1 in the adapter.

The next step is to check the circuit for transmitting data to a programmable chip (D1) and receiving it from it (DO). The source of the transmitted data is the output of the DTR COM port, and the CTS input receives them. If all is well, the CTS logic level should be the inverse of the DTR output. Verify this by changing the latter. The power must be turned on, for example, by a high level at the TXD output.

If the CTS level is independent of the DTR state, measure the voltage at pin 13 of the PIC16F8x board. At a low level of DTR, it should be almost equal to the supply voltage (+5 V), at a high level - no more than 0,5 V. Otherwise, the key on the transistor VT2 of the adapter or the zener diode VD3 of the interface unit is faulty. It should be noted that for programming PICmicro microcontrollers in this zener diode (however, as in VD5) there is no need, they can be safely removed from the circuit.

It is possible that the voltage at pin 13 of the XS1 panel (PIC16F8x) changes within the above limits and enters the correct CTS input, however, the logic level on it is invariably displayed in the TCOM program window as high. This means that the Schmitt trigger on the CTS input of the computer has a negative threshold, and to switch it, it is not enough to reduce the input voltage to almost zero, but a positive value. This situation is within the framework of the RS-232 standard, according to which the thresholds can be within 5:3 V, but a computer with a similar port is unsuitable for working with a programmer assembled according to the scheme in question.

It remains to check the data exchange synchronization signal generation circuit (CLOCK). Its source is the output of the RTS COM port. The jumper between this output and the DSR input is only for the software to verify that the programmer is connected to the port. When changing the state of the RTS, first of all make sure that the state of the DSR always matches it. Then measure the voltage at pin 12 of panel XS1 (PlC16F8x). With a high level at the RTS output, it must be at least 4 V (more precisely, 80% of the microcircuit supply voltage) and not more than 0,6 V exceed the supply voltage. This condition is usually met, since the stabilization voltage of the KS147A (VD6) zener diodes lies in the range of 4,2 ... 5,2 V.

If the voltage is still insufficient (this can happen due to the fact that the above limits correspond to a stabilization current of 10 mA, and in the programmer it is much less), you should either select a zener diode or replace it with a KS147G, designed for a lower current, or with imported with a stabilization voltage of 5,1 V. It is highly undesirable to connect a diode in series with a zener diode (as shown in the diagram by a dashed line). This will cause the zener diode to stop working as a negative voltage limiter (when the DSR output is low) and the protection diode inside the programmable chip will come into action. And although the current through this diode will not reach a dangerous value (due to the resistor R5), it is better to avoid such a mode.

After completing the described checks, we can assume that the hardware of the programmer is working, and proceed to its operation. RopuRgod software and instructions can be "downloaded" at on the website of its author Claudio Lanconelli. On the same site there is a forum where you can ask questions regarding the programmer.

Author: A. Dolgiy, Moscow

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